  This work demonstrated two different kinds of magneto-transport behaviors in
epitaxial $L1_{0}$ MnAl film as a function of temperature. The
magneto-resistance ratio (MR) was negative and exhibited evident enhancement in
the resistivity at coercive fields above 175 K. The MR enhancement was
attributed to the increase of the magnetic domain walls based on the
quantitative correlation between the domain density and the resistivity. Below
175 K, the MR was positive and showed a quadratic dependence on the external
magnetic field, which implied that the MR was dominated by Lorentz effects.
