  The critical temperature for $\alpha$-particle condensation in nuclear matter
with Fermi surface imbalance between protons and neutrons is determined. The
in-medium four-body Schr\"odinger equation, generalizing the Thouless criterion
of the BCS transition, is applied using a Hartree-Fock wave function for the
quartet projected onto zero total momentum in matter with different chemical
potentials for protons and neutrons.
