  We study quantum phase transitions from easy-plane antiferromagnetic metals
to paramagnetic metals in Kondo-Heisenberg lattice systems. If the paramagnetic
metal is a fractionalized Fermi liquid then the universal critical properties
of the phase transition are unaffected for a weak Kondo coupling even when the
Fermi surface intersects the magnetic zone boundary. This is in striking
contrast to the conventional theory of phase transitions between paramagnetic
and antiferromagnetic metals where any Kondo coupling is strongly relevant, and
leads to a Landau-damped `Hertz-Millis' theory. The electron quasi-particle
remains well-defined in the quantum critical regime and the critical spin
fluctuations only contribute subleading corrections to the various properties
of conduction electrons.
