diff --git a/src/underworld3/discretisation.py b/src/underworld3/discretisation.py
index 0a19991f..0bcdb5cf 100644
--- a/src/underworld3/discretisation.py
+++ b/src/underworld3/discretisation.py
@@ -769,6 +769,9 @@ def nuke_coords_and_rebuild(self):
 
         self.dm.copyDS(self.dm_hierarchy[-1])
 
+        # create a kd-tree to store mesh coordinates
+        self._mesh_kdtree = uw.kdtree.KDTree(self.data)
+
         return
 
     @timing.routine_timer_decorator
@@ -2118,12 +2121,8 @@ def rbf_interpolate(self, new_coords, meth=0, p=2, verbose=False, nnn=None, rubb
         with self.mesh.access(self):
             D = self.data.copy()
 
-        if verbose and uw.mpi.rank == 0:
-            print("Building K-D tree", flush=True)
-
-        mesh_kdt = uw.kdtree.KDTree(self.coords)
+        mesh_kdt = self.mesh._mesh_kdtree
         values = mesh_kdt.rbf_interpolator_local(new_coords, D, nnn, p=p, verbose=verbose)
-        del mesh_kdt
 
         return values
 
@@ -2240,10 +2239,9 @@ def write(
     @timing.routine_timer_decorator
     def read_timestep(
         self,
-        data_filename,
         data_name,
         index,
-        outputPath="",
+        outputPath:str,
         verbose=False,
     ):
         """
@@ -2259,8 +2257,7 @@ def read_timestep(
         # mesh.write_timestep( "test", meshUpdates=False, meshVars=[X], outputPath="", index=0)
         # swarm.write_timestep("test", "swarm", swarmVars=[var], outputPath="", index=0)
 
-        output_base_name = os.path.join(outputPath, data_filename)
-        data_file = output_base_name + f".mesh.{data_name}.{index:05}.h5"
+        data_file = outputPath + f"_step_{index:05}.h5"
 
         # check if data_file exists
         if os.path.isfile(os.path.abspath(data_file)):
@@ -2285,7 +2282,7 @@ def field_from_checkpoint(
 
             h5f = h5py.File(data_file)
             D = h5f["fields"][data_name][()].reshape(-1, self.shape[1])
-            X = h5f["fields"]["coordinates"][()].reshape(-1, self.mesh.dim)
+            X = h5f["geometry"]["vertices"][()].reshape(-1, self.mesh.dim)
 
             h5f.close()
 
diff --git a/src/underworld3/kdtree.py b/src/underworld3/kdtree.py
index 3bff6a8c..ab09a879 100644
--- a/src/underworld3/kdtree.py
+++ b/src/underworld3/kdtree.py
@@ -72,7 +72,7 @@ def rbf_interpolator_local_from_kdtree(
         # can decompose weighting vecotrs as IDW is a linear relationship
         # build normalise weight vectors and multiply that with known data
         epsilon   = 1e-12
-        weights   = 1 / np.pow( epsilon+distance_n[:], p)
+        weights   = 1.0 / np.power(epsilon+distance_n[:], p)
         n_weights = (weights.T / np.sum(weights, axis=1)).T
         kdata     = data[closest_n[:]]