  The quantum interference effects induced by the topological phase are studied
analytically in biaxial antiferromagnets with an external magnetic field at an
arbitrarily angle. This study provides a nontrivial generalization of the
Kramers degeneracy for equivalent double-well system to coherently spin
tunneling at ground states as well as low-lying excited states for
antiferromagnetic system with asymmetric twin barriers. The spin-phase
interference effects are found to depend on the orientation of the magnetic
field distinctly.
