diff --git a/Makefile.am b/Makefile.am
index 00622f2..8cb5e01 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -112,6 +112,7 @@ TESTS_C = \
   tests/io_dset_float_text \
   tests/io_dset_int_text \
   tests/io_dset_sparse_text \
+  tests/io_determinant_text \
   tests/io_safe_dset_float_text \
   tests/io_str_text \
   tests/io_dset_str_text \
diff --git a/src/templates_front/build.sh b/src/templates_front/build.sh
index 2ce1136..c7a4d36 100644
--- a/src/templates_front/build.sh
+++ b/src/templates_front/build.sh
@@ -39,6 +39,9 @@ echo "" >> trexio_f.f90
 cat populated/pop_*.c >> trexio.c
 cat populated/pop_*.h >> trexio.h
 
+cat hrw_determinant_front.h >> trexio.h
+cat *_determinant_front.c >> trexio.c
+
 # fortran front end
 cat populated/pop_*.f90  >> trexio_f.f90
 # add helper functions
diff --git a/src/templates_front/templator_front.org b/src/templates_front/templator_front.org
index e321948..473c29c 100644
--- a/src/templates_front/templator_front.org
+++ b/src/templates_front/templator_front.org
@@ -2749,7 +2749,7 @@ trexio_read_$group_dset$(trexio_t* const file,
   if (rc != TREXIO_SUCCESS) return rc;
 
   // introduce a new variable which will be modified with the number of integrals being read if EOF is encountered
-  int64_t eof_read_size = 0UL;
+  int64_t eof_read_size = 0L;
 
   switch (file->back_end) {
 
@@ -4128,18 +4128,16 @@ def delete_$group$(trexio_file) -> None:
 
      #+begin_src c :tangle hrw_determinant_front.h :exports none
 trexio_exit_code trexio_has_determinant_list(trexio_t* const file);
-trexio_exit_code trexio_read_determinant_list(trexio_t* const file, int64_t* const dset);
-trexio_exit_code trexio_write_determinant_list(trexio_t* const file, const int64_t* dset);
 trexio_exit_code trexio_has_determinant_coefficient(trexio_t* const file);
-trexio_exit_code trexio_read_determinant_coefficient(trexio_t* const file, double* const dset);
-trexio_exit_code trexio_write_determinant_coefficient(trexio_t* const file, const double* dset);
+trexio_exit_code trexio_read_determinant_list(trexio_t* const file, const int64_t offset_file, int64_t* const buffer_size, int64_t* const dset);
+trexio_exit_code trexio_write_determinant_list(trexio_t* const file, const int64_t offset_file, const int64_t buffer_size, const int64_t* dset);
      #+end_src
 
 **** Source code for default functions
 
      #+begin_src c :tangle read_determinant_front.c
 trexio_exit_code
-trexio_read_determinant_list (trexio_t* const file, int64_t* const dset)
+trexio_read_determinant_list (trexio_t* const file, const int64_t offset_file, int64_t* const buffer_size, int64_t* const dset)
 {
 
   if (file  == NULL) return TREXIO_INVALID_ARG_1;
@@ -4147,116 +4145,92 @@ trexio_read_determinant_list (trexio_t* const file, int64_t* const dset)
   if (trexio_has_determinant_list(file) != TREXIO_SUCCESS) return TREXIO_DSET_MISSING;
 
   trexio_exit_code rc;
-  int64_t det_dim = 0L;
 
-  rc = trexio_read_determinant_num_64(file, &det_dim);
+  /* Read the number of mos */
+  int64_t mo_num = 0L;
+  rc = trexio_read_mo_num_64(file, &mo_num);
   if (rc != TREXIO_SUCCESS) return rc;
-  if (det_dim == 0L) return TREXIO_INVALID_NUM;
+  if (mo_num == 0L) return TREXIO_INVALID_NUM;
+
+  /* Compute how many integer numbers is needed to represent a determinant */
+  uint32_t int_num = 0;
+  int_num = ((mo_num - 1)/64) + 1;
 
   uint32_t rank = 2;
-  uint64_t dims[2] = {det_dim, 2};
+  uint64_t det_size = (uint64_t) (*buffer_size);
+  uint64_t dims[2] = {det_size, int_num*2UL};
 
-  assert(file->back_end < TREXIO_INVALID_BACK_END);
+  // introduce a new variable which will be modified with the number of integrals being read if EOF is encountered
+  int64_t eof_read_size = 0L;
 
-  rc = TREXIO_FAILURE;
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_read_determinant_list(file, dset, rank, dims);
+    rc = trexio_text_read_determinant_list(file, offset_file, rank, dims, &eof_read_size, dset); 
     break;
 
   case TREXIO_HDF5:
 #ifdef HAVE_HDF5
-    return trexio_hdf5_read_determinant_list(file, dset, rank, dims);
+    rc = -1; //trexio_hdf5_read_determinant_list(file, offset_file, rank, dims, &eof_read_size, dset);
     break;
 #else
-    return TREXIO_BACK_END_MISSING;
+    rc = TREXIO_BACK_END_MISSING;
     break;
 #endif
 /*
   case TREXIO_JSON:
-    return trexio_json_read_
+    return trexio_json_read_$group_dset$(...);
     break;
 ,*/
+  default:
+    rc = TREXIO_FAILURE;  /* Impossible case */
+    break;
   }
 
+  if (rc != TREXIO_SUCCESS && rc != TREXIO_END) return rc;
+
+  if (rc == TREXIO_END) *buffer_size = eof_read_size;
+
+  return rc; 
+
 }
 
-trexio_exit_code
-trexio_read_determinant_coefficient (trexio_t* const file, double* const dset)
-{
-
-  if (file  == NULL) return TREXIO_INVALID_ARG_1;
-  if (dset  == NULL) return TREXIO_INVALID_ARG_2;
-  if (trexio_has_determinant_coefficient(file) != TREXIO_SUCCESS) return TREXIO_DSET_MISSING;
-
-  trexio_exit_code rc;
-  int64_t det_dim = 0L;
-
-  rc = trexio_read_determinant_num_64(file, &det_dim);
-  if (rc != TREXIO_SUCCESS) return rc;
-  if (det_dim == 0L) return TREXIO_INVALID_NUM;
-
-  uint32_t rank = 1;
-  uint64_t dims[1] = {det_dim};
-
-  assert(file->back_end < TREXIO_INVALID_BACK_END);
-
-  rc = TREXIO_FAILURE;
-  switch (file->back_end) {
-
-  case TREXIO_TEXT:
-    return trexio_text_read_determinant_coefficient(file, dset, rank, dims);
-    break;
-
-  case TREXIO_HDF5:
-#ifdef HAVE_HDF5
-    return trexio_hdf5_read_determinant_coefficient(file, dset, rank, dims);
-    break;
-#else
-    return TREXIO_BACK_END_MISSING;
-    break;
-#endif
-/*
-  case TREXIO_JSON:
-    return trexio_json_read_
-    break;
-,*/
-  }
-
-}
      #+end_src
 
      #+begin_src c :tangle write_determinant_front.c
 trexio_exit_code
-trexio_write_determinant_list (trexio_t* const file, const int64_t* dset)
+trexio_write_determinant_list (trexio_t* const file, const int64_t offset_file, const int64_t buffer_size, const int64_t* dset)
 {
 
   if (file == NULL) return TREXIO_INVALID_ARG_1;
   if (dset == NULL) return TREXIO_INVALID_ARG_2;
 
   trexio_exit_code rc;
-  int64_t det_dim = 0L;
 
-  rc = trexio_read_determinant_num_64(file, &det_dim);
+  /* Read the number of mos */
+  int64_t mo_num = 0L;
+  rc = trexio_read_mo_num_64(file, &mo_num);
   if (rc != TREXIO_SUCCESS) return rc;
-  if (det_dim == 0L) return TREXIO_INVALID_NUM;
+  if (mo_num == 0L) return TREXIO_INVALID_NUM;
+
+  /* Compute how many integer numbers is needed to represent a determinant */
+  uint32_t int_num = 0;
+  int_num = ((mo_num - 1)/64) + 1;
 
   uint32_t rank = 2;
-  uint64_t dims[2] = {det_dim, 2};
+  uint64_t dims[2] = {buffer_size, int_num*2UL};
 
   assert(file->back_end < TREXIO_INVALID_BACK_END);
 
-  rc = TREXIO_FAILURE;
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_write_determinant_list(file, dset, rank, dims);
+    return trexio_text_write_determinant_list(file, offset_file, rank, dims, dset);
     break;
 
   case TREXIO_HDF5:
 #ifdef HAVE_HDF5
-    return trexio_hdf5_write_determinant_list(file, dset, rank, dims);
+    return -1; //trexio_hdf5_write_determinant_list(file, dset, rank, dims);
     break;
 #else
     return TREXIO_BACK_END_MISSING;
@@ -4271,47 +4245,6 @@ trexio_write_determinant_list (trexio_t* const file, const int64_t* dset)
 
 }
 
-trexio_exit_code
-trexio_write_determinant_coefficient (trexio_t* const file, const double* dset)
-{
-
-  if (file == NULL) return TREXIO_INVALID_ARG_1;
-  if (dset == NULL) return TREXIO_INVALID_ARG_2;
-
-  trexio_exit_code rc;
-  int64_t det_dim = 0L;
-
-  rc = trexio_read_determinant_num_64(file, &det_dim);
-  if (rc != TREXIO_SUCCESS) return rc;
-  if (det_dim == 0L) return TREXIO_INVALID_NUM;
-
-  uint32_t rank = 1;
-  uint64_t dims[1] = {det_dim};
-
-  assert(file->back_end < TREXIO_INVALID_BACK_END);
-
-  rc = TREXIO_FAILURE;
-  switch (file->back_end) {
-
-  case TREXIO_TEXT:
-    return trexio_text_write_determinant_coefficient(file, dset, rank, dims);
-    break;
-
-  case TREXIO_HDF5:
-#ifdef HAVE_HDF5
-    return trexio_hdf5_write_determinant_coefficient(file, dset, rank, dims);
-    break;
-#else
-    return TREXIO_BACK_END_MISSING;
-    break;
-#endif
-/*
-  case TREXIO_JSON:
-    return trexio_json_read_
-    break;
-,*/
-  }
-}
      #+end_src
 
      #+begin_src c :tangle has_determinant_front.c
@@ -4326,11 +4259,11 @@ trexio_has_determinant_list (trexio_t* const file)
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_has_determinant_list(file)
+    return trexio_text_has_determinant_list(file);
 
   case TREXIO_HDF5:
 #ifdef HAVE_HDF5
-    return trexio_hdf5_has_determinant_list(file);
+    return -1; //trexio_hdf5_has_determinant_list(file);
 #else
     return TREXIO_BACK_END_MISSING;
 #endif
@@ -4355,11 +4288,11 @@ trexio_has_determinant_coefficient (trexio_t* const file)
   switch (file->back_end) {
 
   case TREXIO_TEXT:
-    return trexio_text_has_determinant_coefficient(file)
+    return -1; //trexio_text_has_determinant_coefficient(file);
 
   case TREXIO_HDF5:
 #ifdef HAVE_HDF5
-    return trexio_hdf5_has_determinant_coefficient(file);
+    return -1; //trexio_hdf5_has_determinant_coefficient(file);
 #else
     return TREXIO_BACK_END_MISSING;
 #endif
diff --git a/src/templates_text/build.sh b/src/templates_text/build.sh
index 9e28511..b5d73f6 100644
--- a/src/templates_text/build.sh
+++ b/src/templates_text/build.sh
@@ -10,6 +10,9 @@ cat populated/pop_struct_text_group_dset.h >> trexio_text.h
 cat populated/pop_struct_text_group.h >> trexio_text.h
 cat basic_text.h   >> trexio_text.h
 
+cat hrw_determinant_text.h >> trexio_text.h
+cat *_determinant_text.c >> trexio_text.c
+
 cat populated/pop_free_group_text.c >> trexio_text.c
 cat populated/pop_read_group_text.c >> trexio_text.c
 cat populated/pop_flush_group_text.c >> trexio_text.c
diff --git a/src/templates_text/templator_text.org b/src/templates_text/templator_text.org
index 066fd85..c44ce4f 100644
--- a/src/templates_text/templator_text.org
+++ b/src/templates_text/templator_text.org
@@ -1313,6 +1313,182 @@ trexio_text_delete_$group$ (trexio_t* const file)
 }
    #+end_src
 
+** Source code for the determinant part 
+
+   Each array is stored in a separate =.txt= file due to the fact that determinant I/O has to be decoupled
+   from conventional write/read/flush behaviour of the TEXT back end. Chunks are used to read/write the data
+   to prevent memory overflow. Chunks have a given ~int64_t size~.
+   Size specifies the number of data items, e.g. determinants.
+
+
+   #+begin_src c :tangle hrw_determinant_text.h :exports none
+trexio_exit_code trexio_text_has_determinant_list(trexio_t* const file);
+trexio_exit_code trexio_text_read_determinant_list(trexio_t* const file, const int64_t offset_file, const uint32_t rank, const uint64_t* dims, int64_t* const eof_read_size, int64_t* const list);
+trexio_exit_code trexio_text_write_determinant_list(trexio_t* const file, const int64_t offset_file, const uint32_t rank, const uint64_t* dims, const int64_t* list);
+   #+end_src
+
+   #+begin_src c :tangle read_determinant_text.c
+trexio_exit_code trexio_text_read_determinant_list(
+                                               trexio_t* const file,
+                                               const int64_t offset_file,
+                                               const uint32_t rank,
+                                               const uint64_t* dims,
+                                               int64_t* const eof_read_size,
+                                               int64_t* const list) 
+{
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+  if (eof_read_size == NULL) return TREXIO_INVALID_ARG_5;
+
+  const char determinant_list_file_name[256] = "/determinant_list.txt";
+  /* The full path to the destination TXT file with sparse data. This will include TREXIO directory name. */
+  char file_full_path[TREXIO_MAX_FILENAME_LENGTH];
+
+  /* Copy directory name in file_full_path */
+  strncpy (file_full_path, file->file_name, TREXIO_MAX_FILENAME_LENGTH);
+  /* Append name of the file with sparse data */
+  strncat (file_full_path, determinant_list_file_name,
+           TREXIO_MAX_FILENAME_LENGTH-strlen(determinant_list_file_name));
+
+  /* Open the file in "r" (read) mode to guarantee that no truncation happens upon consecutive reads */
+  FILE* f = fopen(file_full_path, "r");
+  if(f == NULL) return TREXIO_FILE_ERROR;
+
+  /* Specify the line length in order to offset properly. 
+     Each 64-bit integer takes at most 10 slots and requires one space, 
+     we have int_num integers per up-spin determinant, 
+     then this number is doubled because we have the same number for down-spin electrons,
+     and then one newline char.
+   ,*/
+  uint64_t line_length = 6UL*10UL + 6UL; // + 6UL + 1UL; // dims[1]*11UL + 1UL;
+
+  /* Offset in the file according to the provided  value of offset_file and optimal line_length */
+  fseek(f, (long) offset_file * line_length, SEEK_SET);
+
+  /* Read the data from the file and check the return code of fprintf to verify that > 0 bytes have been read or reached EOF */
+  int rc;
+
+  //char buffer[16];
+  char* buffer = CALLOC(line_length+1, char);
+  
+  uint64_t count = 0UL;
+  int shift = 0;
+  uint64_t accum = 0UL;
+  for (uint64_t i=0UL; i < (uint64_t) dims[0]; ++i) {
+
+      accum = 0UL;
+      memset(buffer, 0, line_length+1); // sizeof(buffer)); //1024);
+
+      if(fgets(buffer, line_length, f) == NULL){
+
+        fclose(f);
+        FREE(buffer);
+        *eof_read_size = count;
+        return TREXIO_END;
+
+      } else {
+
+  /* The format string is not anymore static but rather dynamic (the number of ints depend on the mo_num) 
+     Thus, we parse the buffer string int_num*2 times to get the bit field determinants. 
+  */
+        
+        for (int32_t j=0; j<dims[1]; ++j) {
+          rc = sscanf(buffer, "%10" SCNd64 "%n", list + i + j, &shift);
+          if(rc <= 0) {
+            fclose(f);
+            FREE(buffer);
+            return TREXIO_FAILURE;
+          }
+          buffer += shift;
+          accum += shift;
+        }
+ 
+        count += 1UL;
+        buffer -= accum;
+      }
+  }
+
+  FREE(buffer);
+ 
+  /* Close the TXT file */
+  rc = fclose(f);
+  if(rc != 0) return TREXIO_FILE_ERROR;
+
+  return TREXIO_SUCCESS;
+}
+   #+end_src
+
+   #+begin_src c :tangle write_determinant_text.c
+trexio_exit_code trexio_text_write_determinant_list(trexio_t* const file,
+                                                const int64_t offset_file,
+						const uint32_t rank,
+                                                const uint64_t* dims,
+                                                const int64_t* list) 
+{
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  const char determinant_list_file_name[256] = "/determinant_list.txt";
+  /* The full path to the destination TXT file with sparse data. This will include TREXIO directory name. */
+  char file_full_path[TREXIO_MAX_FILENAME_LENGTH];
+
+  /* Copy directory name in file_full_path */
+  strncpy (file_full_path, file->file_name, TREXIO_MAX_FILENAME_LENGTH);
+  /* Append name of the file with sparse data */
+  strncat (file_full_path, determinant_list_file_name,
+           TREXIO_MAX_FILENAME_LENGTH-strlen(determinant_list_file_name));
+
+  /* Open the file in "a" (append) mode to guarantee that no truncation happens upon consecutive reads */
+  FILE* f = fopen(file_full_path, "a");
+  if(f == NULL) return TREXIO_FILE_ERROR;
+
+  /* Write the data in the file and check the return code of fprintf to verify that > 0 bytes have been written */
+  int rc;
+  for (uint64_t i=0UL; i < dims[0]; ++i) {
+    
+    /* The loop below is needed to write a line with int bit fields for alpha and beta electrons */
+    for (uint32_t j=0; j < (uint32_t) dims[1]; ++j) {
+      rc = fprintf(f, "%10" PRId64 " ", *(list + i + j));
+      if(rc <= 0) {
+        fclose(f);
+        return TREXIO_FAILURE;
+      }
+    }
+    fprintf(f, "%s", "\n");
+    
+  }
+
+  /* Close the TXT file */
+  rc = fclose(f);
+  if (rc != 0) return TREXIO_FILE_ERROR;
+
+  /* Exit upon success */
+  return TREXIO_SUCCESS;
+}
+   #+end_src
+
+   #+begin_src c :tangle has_determinant_text.c
+trexio_exit_code trexio_text_has_determinant_list(trexio_t* const file)
+{
+  if (file == NULL) return TREXIO_INVALID_ARG_1;
+
+  const char determinant_list_file_name[256] = "/determinant_list.txt";
+  /* The full path to the destination TXT file with sparse data. This will include TREXIO directory name. */
+  char file_full_path[TREXIO_MAX_FILENAME_LENGTH];
+
+  /* Copy directory name in file_full_path */
+  strncpy (file_full_path, file->file_name, TREXIO_MAX_FILENAME_LENGTH);
+  /* Append name of the file with sparse data */
+  strncat (file_full_path, determinant_list_file_name,
+           TREXIO_MAX_FILENAME_LENGTH-strlen(determinant_list_file_name));
+
+  /* Check the return code of access function to determine whether the file with data exists or not */
+  if (access(file_full_path, F_OK) == 0){
+    return TREXIO_SUCCESS;
+  } else {
+    return TREXIO_HAS_NOT;
+  }
+}
+   #+end_src
+
 * Constant file suffixes (not used by the generator)               :noexport:
 
   #+begin_src c :tangle suffix_text.h
diff --git a/tools/generator.py b/tools/generator.py
index 9904921..3562eb8 100644
--- a/tools/generator.py
+++ b/tools/generator.py
@@ -4,6 +4,7 @@ from generator_tools import *
 # --------------------- GET CONFIGURATION FROM THE TREX.JSON ---------------- #
 config_file = 'trex.json'
 trex_config = read_json(config_file)
+trex_config.pop('determinant')
 # --------------------------------------------------------------------------- #
 
 # -------------------- GET ATTRIBUTES FROM THE CONFIGURATION ---------------- #