Linear magnetoresistance of hetroepitaxial thin films of pyrochlore iridates Bi$_2$Ir$_2$O$_7$

We report on the discovery of linear magnetoresistance in hetroepitaxial thin films of the pyrochlore iridates Bi$_2$Ir$_2$O$_7$. The magnetoresistance of Bi$_2$Ir$_2$O$_7$ shows a highly isotropic, linear field dependence at T = 1.6K, but gradually evolves towards a quadratic field dependence as temperature increases. By interfacing the Bi$_2$Ir$_2$O$_7$ with pyrochlore spin ice compound Dy$_2$Ti$_2$O$_7$, the magnetoresistance at sub-kelvin temperatures shows pronounce anisotropy with a complex field dependence. We argued that these unusual magnetotransport behaviors cannot be explained by disorder induced quantum correction, but might be related to the magnetism of Bi$_2$Ir$_2$O$_7$.