diff --git a/api/rpk-api/firm/contract/models.py b/api/rpk-api/firm/contract/models.py
index 43cdc48..aa9967c 100644
--- a/api/rpk-api/firm/contract/models.py
+++ b/api/rpk-api/firm/contract/models.py
@@ -27,11 +27,11 @@ class ContractDraftStatus(str, Enum):
 
 
 class DraftParty(BaseModel):
-    entity_id: PydanticObjectId = ForeignKey("entities", "Entity", default="", title="Partie")
-    entity: SkipJsonSchema[Entity] = Field(default=None, exclude=True, )
+    entity_id: Optional[PydanticObjectId] = ForeignKey("entities", "Entity", default=None, title="Partie")
     part: str = Field(title="Rôle")
-    representative_id: PydanticObjectId = ForeignKey("entities", "Entity", default="", title="Représentant")
+    representative_id: Optional[PydanticObjectId] = ForeignKey("entities", "Entity", default=None, title="Représentant")
 
+    entity: SkipJsonSchema[Entity] = Field(default=None, exclude=True, )
     class Config:
         title = 'Partie'
 
@@ -64,7 +64,7 @@ class ContractProvisionTemplateReference(BaseModel):
         "ProvisionTemplate",
         displayed_fields=['title', 'body'],
         props={"parametrized": True},
-        default="",
+        default=None,
         title="Template de clause"
     )
 
diff --git a/api/rpk-api/firm/entity/models.py b/api/rpk-api/firm/entity/models.py
index e5abbf3..61066a9 100644
--- a/api/rpk-api/firm/entity/models.py
+++ b/api/rpk-api/firm/entity/models.py
@@ -4,7 +4,7 @@ from typing import List, Literal, Optional
 from pydantic import Field, BaseModel
 from beanie import Indexed, PydanticObjectId
 
-from firm.core.models import CrudDocument
+from firm.core.models import CrudDocument, ForeignKey
 from firm.core.filter import Filter, FilterSchema
 
 
@@ -39,16 +39,7 @@ class Individual(EntityType):
 
 class Employee(BaseModel):
     position: Indexed(str) = Field(title='Poste')
-    entity_id: PydanticObjectId = Field(
-        foreignKey={
-            "reference": {
-                "resource": "entities",
-                "schema": "Entity",
-                "condition": "entity_data.type=individual"
-            }
-        },
-        title='Employé'
-    )
+    entity_id: PydanticObjectId = ForeignKey("entities", "Entity", title='Employé')
 
     class Config:
         title = 'Fiche Employé'
diff --git a/api/rpk-api/firm/template/models.py b/api/rpk-api/firm/template/models.py
index 5cb03a6..7e4c781 100644
--- a/api/rpk-api/firm/template/models.py
+++ b/api/rpk-api/firm/template/models.py
@@ -1,35 +1,17 @@
-from typing import List
+from typing import List, Optional
 from html import unescape
 
 from beanie import PydanticObjectId
 from pydantic import BaseModel, Field
 
-from firm.core.models import CrudDocument, RichtextMultiline, RichtextSingleline, DictionaryEntry
+from firm.core.models import CrudDocument, RichtextMultiline, RichtextSingleline, DictionaryEntry, ForeignKey
 from firm.core.filter import Filter, FilterSchema
 
 
 class PartyTemplate(BaseModel):
-    entity_id: PydanticObjectId = Field(
-        foreignKey={
-            "reference": {
-                "resource": "entities",
-                "schema": "Entity",
-            }
-        },
-        default="",
-        title="Partie"
-    )
+    entity_id: Optional[PydanticObjectId] = ForeignKey("entities", "Entity", default=None, title="Partie")
     part: str = Field(title="Rôle")
-    representative_id: PydanticObjectId = Field(
-        foreignKey={
-            "reference": {
-                "resource": "entities",
-                "schema": "Entity",
-            }
-        },
-        default="",
-        title="Représentant"
-    )
+    representative_id: Optional[PydanticObjectId] = ForeignKey("entities", "Entity", default=None, title="Représentant")
 
     class Config:
         title = 'Partie'
@@ -62,14 +44,10 @@ class ProvisionTemplate(CrudDocument):
 
 
 class ProvisionTemplateReference(BaseModel):
-    provision_template_id: PydanticObjectId = Field(
-        foreignKey={
-            "reference": {
-                "resource": "templates/provisions",
-                "schema": "ProvisionTemplate",
-                "displayedFields": ['title', 'body']
-            },
-        },
+    provision_template_id: PydanticObjectId = ForeignKey(
+        "templates/provisions",
+        "TemplateProvision",
+        ['title', 'body'],
         props={"parametrized": True},
         title="Template de clause"
     )