Magneto-transport properties in All-in-All-out magnetic ordered epitaxial Sm$_{2}$Ir$_{2}$O$_{7}$ and Nd$_{2}$Ir$_{2}$O$_{7}$ films.

Pyrochlore iridates R$_{2}$Ir$_{2}$O$_{7}$ (R$=$rare earth element) have been predicted to exhibit a variety of exotic physical phenomena, such as the Weyl semimetallic state and topologically insulating behavior with all-in-all-out (AIAO) magnetic ordering. Here, we have observed a metal-insulator transition accompanied by the AIAO-type magnetic ordering in both Nd$_{2}$Ir$_{2}$O$_{7}$ and Sm$_{2}$Ir$_{2}$O$_{7}$ films below their respective ordering temperatures. Negative magnetoresistance (MR) is observed below 20 K and this gradually transitions into positive MR upon warming. We speculate that this characteristic negative MR is related to the $f$-$d$ exchange coupling between the electrons at the Ir sites and localized moments at the R sites, which induces magnetic ordering on the R sub-lattice. Another remarkable feature is unconventional domain wall (DW) conductance. AIAO-type magnetic DW shows metallic behavior in Nd$_{2}$Ir$_{2}$O$_{7}$ while Sm$_{2}$Ir$_{2}$O$_{7}$ shows insulating behavior. This AIAO-type metallic (insulating) DW conductance is thought to be closely related to the existence of Weyl-semimetallic state (Mott insulating state) which is consistent with a recent theoretical prediction.