  Giant oscillations of the conductance of a superconductor - ferromagnet -
superconductor Andreev interferometer are predicted. The effect is due to the
resonant transmission of normal electrons through Andreev levels when the
voltage $V$ applied to the ferromagnet is close to $2h_0/e$ ($h_0$ is the
spin-dependant part of the electron energy). The effect of bias voltage and
phase difference between the superconductors on the current and the
differential conductance is presented. These efects allow a direct spectroscopy
of Andreev levels in the ferromagnet.
