  We consider a correlated wavefunction including particle-hole pairing at half
a reciprocal lattice vector for itinerant electrons hopping on a square lattice
in two dimensions and subject both to on-site and nearest-neighbor repulsion.
We find, within mean field theory, that in a suitable range of parameters there
is a tendency toward a novel form of ordering characterized by discrete
symmetry breaking and a gap at the magnetic zone boundary, which supports
hole-like semiconductor behavior near half filling despite an apparently normal
Fermi surface. The effective quasiparticle couplings to phonons includes a
significant d-wave piece, which plausibly leads to an especially robust
tendency toward superconductivity.
