  The prospect of a Dirac half metal, a material which is characterized by a
bandstructure with a gap in one spin channel but a Dirac cone in the other, is
of both fundamental interest and a natural candidate for use in spin-polarized
current applications. However, while the possibility of such a material has
been reported based on model calculations[H. Ishizuka and Y. Motome, Phys. Rev.
Lett. 109, 237207 (2012)], it remains unclear what material system might
realize such an exotic state. Using first-principles calculations, we show that
the experimentally accessible Mn intercalated epitaxial graphene on SiC(0001)
transits to a Dirac half metal when the coverage is > 1/3 monolayer. This
transition results from an orbital-selective breaking of quasi-2D inversion
symmetry, leading to symmetry breaking in a single spin channel which is robust
against randomness in the distribution of Mn intercalates. Furthermore, the
inclusion of spin-orbit interaction naturally drives the system into the
quantum anomalous Hall (QAH) state. Our results thus not only demonstrate the
practicality of realizing the Dirac half metal beyond a toy model but also open
up a new avenue to the realization of the QAH effect.
