  The gapless surface Dirac cone of time reversal invariant topological
insulators is protected by time reversal symmetry due to the Kramers' theorem.
Spin degree of freedom is usually required since Kramers' theorem only
guarantees double degeneracy for spinful fermions, but not for spinless
fermions. In this paper, we present an antiferromagnetic spinless model, which
breaks time reversal symmetry. Similar to time reversal invariant topological
insulators, this model possesses a topologically non-trivial phase with a
single surface Dirac cone, which is protected by the combination of time
reversal and translation operation. Our results show that in magnetic crystals,
a single Dirac cone can exist on the surface even without any spin degree of
freedom and spin-orbit coupling.
