  Phase transitions involving spontaneous time-reversal symmetry breaking are
studied on the honeycomb lattice at finite hole-doping with
next-nearest-neighbor repulsion. We derive an exact expression for the
mean-field equation of state in closed form, valid at temperatures much less
than the Fermi energy. Contrary to standard expectations, we find that
thermally induced intraband particle-hole excitations can create and stabilize
a uniform metallic phase with broken time-reversal symmetry as the temperature
is "raised" in a region where the groundstate is a trivial metal.
