  The response is studied of a narrow-band conductor with bcc lattice to a
low-frequency signal under presence of a high-frequency signal. In a high
enough dc electric field Ex, the conduction electrons form a bistable system,
which results in spontaneous appearance of a transverse electric field Ey. Ac
field along y axis leads to amplification of the low-frequency signal with
non-monotonous dependence of the gain on the high-frequency field amplitude, so
that vibrational resonance takes place. Besides, high-frequency field induced
nonequilibrium phase transition is found.
