  We consider a mixture of two-species atomic Bose-Einstein codensates coupled
to a bound molecular state at zero temperature via interspecies Feshbach
resonance. The interspecies Feshbach coupling precludes the possibility of
doubly mixed phases while enables not only the pure molecular superfluid but
also the pure atomic superfluids to exist as distinct phases. We show that this
system is able to support a rich set of phase separations, including that
between two distinct mixed atom-molecule phases. We pay particular attention to
the effects of the Feschbach coupling and the particle collisions on the
miscibility of this multi-component condensate system.
