Fermi-surface Reconstruction at the Metamagnetic High-Field Transition in Uranium Mononitride

We report on the electronic and thermodynamic properties of the antiferromagnetic metal uranium mononitride with a Neel temperature T-N approximate to 53 K. The fabrication of microstructures from single crystals enables us to study the low-temperature metamagnetic transition at approximately 58 T by high-precision magnetotransport, Hall-effect, and magnetic-torque measurements. We confirm the evolution of the high-field transition from a broad and complex behavior to a sharp first-order-like step, associated with a spin flop at low temperature. In the high-field state, the magnetic contribution to the temperature dependence of the resistivity is suppressed completely. It evolves into an almost quadratic dependence at low temperatures indicative of a metallic character. Our detailed investigation of the Hall effect provides evidence for a prominent Fermi-surface reconstruction as the system is pushed into the high-field state.