CST - Modelling Nichrome coating on copper

CST Studio Suite  

Hi,

I want to model a thin layer (100 nm) of NiCr on copper. What is the best way to do this? I already tried to do it with the "Coating" option inside the copper material properties. But you can only use a material of type "normal" for the coating, so I am not sure if this is an accurate way to model a metal coating. The simulation frequency is around 78 GHz.