  We theoretically investigate the magnetotransport of Dirac fermions coupled
with localized moments to understand the physical properties of the Dirac
material EuMnBi$_2$. Using an interlayer hopping form, which simplifies the
complicated interaction between the layers of Dirac fermions and the layers of
magnetic moments in EuMnBi$_2$, the theory reproduces most of the features
observed in this system. The hysteresis observed in EuMnBi$_2$ can be caused by
the valley splitting that is induced by the spin-orbit coupling and the
external magnetic field with the molecular field created by localized moments.
Our theory suggests that the magnetotransport in EuMnBi$_2$ is due to the
interplay among Dirac fermions, localized moments, and spin-orbit coupling.
