  We analyze the model of an atomic Bose-Einstein condensate (BEC)
parametrically coupled to a molecular BEC via a photoassociation process. We
show that an interplay of nonlinear inter- and intra-species interactions leads
to the formation of mutually trapped states of a hybrid condensate, which are
spatially localized even without a trap. The untrapped atomic-molecular
condensates with a large number of atoms in either fraction are shown to be
dynamically stable in the framework of a mean field theory.
