  We theoretically analyzed the microwave-induced modification of the Hall
magnetoresistivity in high mobility two-dimensional electron systems. These
systems present diagonal magnetoresistivity oscillations and zero-resistance
states when are subjected to microwave radiation. The most surprising
modification of the Hall magnetoresistivity is a periodic reduction which
correlates with a periodic increase in the diagonal resistivity. We present a
model that explains the experimental results considering that radiation affects
directly only the diagonal resistivity and the observed Hall resistivity
changes are coming from the tensor relationship between both of them.
