  The amplitude of magnetoresistance quantum oscillations of Al and Be point
contacts in a magnetic field parallel to the contact axis has been studied as a
function of voltage applied over the contact. It was found that for one group
of contacts the oscillation amplitude nonmonotonously increases with the bias
voltage increase, while for the other part of the contacts a decrease of
amplitude was observed. The scattering of electrons with nonequilibrium phonons
and also phonon-phonon collisions will be discussed as the possible reasons of
the observed effects.
