not-so-sparse Conductivity tensor in hfss

I am looking for a way to set up a conductivity tensor with off-diagonal terms in hfss. I am not aware of a way to do this directly. You can only have xx,yy and zz terms - in other words you can have a diagonal conductivity matrix. However, with off-diagonal terms you get coupling between directions. That is, an E field in the x-direction induces a current in the y-direction. Maybe there is a way to "trick" hfss into doing it. It seems that somehow hfss does this with magnetic permeability since a biased ferrite will rotate a wave. Any thoughts on, or experience with, accomplishing this with conductivity?