  We have studied the effect of an in-plane magnetic field on Hall
field-induced resistance oscillations in high mobility two-dimensional electron
systems. We have found that the oscillation frequency depends only on the
perpendicular component of the magnetic field but the oscillation amplitude
decays exponentially with an in-plane component. While these findings cannot be
accounted for by existing theories of nonlinear transport, our analysis
suggests that the decay can be explained by an in-plane magnetic field-induced
modification of the quantum scattering rate.
