diff --git a/CI/Determinant.ml b/CI/Determinant.ml
index 6d7c342..ff62d3e 100644
--- a/CI/Determinant.ml
+++ b/CI/Determinant.ml
@@ -1,86 +1,40 @@
-type phase_type =
-| Plus
-| Minus
-
-type spin_determinant_type =
+type t =
 {
-  bitstring : Z.t ;
-  phase  : phase_type;
-}
-
-type determinant_type =
-{
-  alpha : Z.t ;
-  beta  : Z.t ;
-  phase  : phase_type;
+  alpha : Spindeterminant.t ;
+  beta  : Spindeterminant.t ;
 }
 
 
-type t = determinant_type
+
+let alpha t = t.alpha
+
+let beta  t = t.beta 
+
+let phase t = 
+  match Spindeterminant.(phase t.alpha, phase t.beta) with
+  | Phase.Pos, Phase.Pos 
+  | Phase.Neg, Phase.Neg  -> Phase.Pos
+  | _ -> Phase.Neg
 
 
-let spindet_of_list l = 
-  let rec aux accu nperm = function
-  | [] -> accu, if nperm mod 2 = 0 then Plus else Minus
-  | i :: rest -> 
-    let i = pred i in
-    let x = Z.(shift_left one i) in
-    let accu = Z.logor accu x in
-    let nperm =
-      let mask = Z.(x-one) in
-      let r = Z.logand accu mask in
-      if r = Z.zero then
-        nperm
-      else
-        nperm + (Z.popcount r)
-    in
-    aux accu nperm rest
-  in
-  List.rev l
-  |> aux Z.zero 0
-
-
-
-(* TODO Phase *)
-let rec to_list spindet =
-  let rec aux accu z =
-    if z <> Z.zero then
-      let element = (Z.(trailing_zeros z)+1) in
-      aux (element::accu) Z.(z land (pred z))
-    else List.rev accu
-  in aux [] spindet
-  
+let of_spindeterminants a b =
+  {
+    alpha = a ;
+    beta  = b
+  }
 
 let of_lists a b =
-  let alpha, phase_a = 
-    spindet_of_list a
-  in
-  let beta, phase_b = 
-    spindet_of_list b
-  in
-  let phase =
-    match phase_a, phase_b with
-    | Plus , Plus -> Plus
-    | Minus, Minus-> Plus
-    | _ -> Minus
-  in
-  { alpha ; beta ; phase }
-
-let alpha det = det.alpha
-let beta  det = det.beta
-
-let sgn det =
-  match det.phase with
-  | Plus  ->  1.
-  | Minus -> -1.
-
-let pp_spindet ppf spindet =
-  String.init (Z.numbits spindet) (fun i -> if (Z.testbit spindet i) then '+' else '-')
-  |> Format.fprintf ppf "@[<v> @[<h> %s @]@]"
+  {
+    alpha = Spindeterminant.of_list a ;
+    beta  = Spindeterminant.of_list b
+  }
 
 
-let pp_det ppf det =
-  Format.fprintf ppf "@[<v> a: %a @; b: %a @]@." pp_spindet det.alpha pp_spindet det.beta
+let pp_det ppf t =
+  Format.fprintf ppf "@[<v> a: %a @; b: %a @]@."
+    Spindeterminant.pp_spindet t.alpha
+    Spindeterminant.pp_spindet t.beta
+
 
 let test_case () =