Can't I apply different materials to different mesh instances (model tree- different entities) in a FEM representation using 3DEXPERIENCE Structural Model Prep app?

When I try to apply a material, it gets applied to an entire FEM representation. That means same material is applied to all entities present in the FEM rep. Now, as I can export only one FEM rep. at a time, I can not export a mesh model with different materials applied to its different components/shells!