The resonances a t microwave frequencies can be observed in polarized junctions ; this was studied in previous papers and we have called for an important contribution of minority carriers. With a magnetic field B, a non diagonal component of the electrical conductivity can exist, a sort of microwave Hall effect. This can be considered as the effect of the non-diagonal part of the microwave susceptibility along the E A B direction. We report the observation of this non-diagonal component, which allows to verify the sign of the charge carriers. This experiment can be considered as a generalization of the d.c. Hall effect.