diff --git a/models/model_bfg.py b/models/model_bfg.py
index bc03937..395a967 100644
--- a/models/model_bfg.py
+++ b/models/model_bfg.py
@@ -92,7 +92,11 @@ def build_bfg(
             continue
 
         if 'XY' in intr.label:
-            intr.cpl           = -Jperp
+            # Nicole's U1 Sp/Sm are spherical components:
+            # Sp = -S+ / sqrt(2), Sm = S- / sqrt(2). The two tensor
+            # products therefore carry a factor 1/2, so use -2*Jperp
+            # to implement -Jperp * (S+_i S-_j + S-_i S+_j).
+            intr.cpl           = -2.0 * Jperp
             intr.leading_tnsr  = xy4.clone()
             intr.terminal_tnsr = xy4dag.clone()
             if intr.terminal_site > intr.leading_site + 1:
diff --git a/registry.yaml b/registry.yaml
index e77acf8..bb3bf87 100644
--- a/registry.yaml
+++ b/registry.yaml
@@ -7,7 +7,7 @@ categories:
       - name: model_bfg
         file: models/model_bfg.py
         description: Balents-Fisher-Girvin model builder for Alice
-        sha256: 41e246e3edfb2bc7a0a117a4bd9c1570984acb8fe5eee9d5c882aa13b09e6d24
+        sha256: 5a3282ae34a5d68171bf60c45d45acc4683ef0fb3e3b46a8599d4ea3e59f9711
 
   intrcmaps:
     description: Interaction maps for Alice