  We study a singlet-triplet Josephson junction between a conventional s-wave
superconductor and an unconventional p$_{\rm x}$-wave superconductor. The
Andreev spectrum of the junction yields a spontaneous magnetization in
equilibrium. This allows manipulating the occupation of the Andreev levels
using an ac Zeeman field. The induced Rabi oscillations manifest themselves as
a resonance in the current-phase relation. For a circularly polarized magnetic
field, we find a spin selection rule, yielding Rabi oscillations only in a
certain interval of the superconducting phase difference.
