Pressure driven collapse of the magnetism in the Kondo insulator UNiSn

The effect of pressure on the electronic and magnetic properties of the antiferromagnetic (T _N∼43 K) narrow gap semiconductor UNiSn has been investigated by ¹¹⁹Sn Mössbauer spectroscopy and nuclear forward scattering of synchrotron radiation, electrical resistance, and x-ray diffraction. We show that the decrease of the semiconducting gap which leads to a metallic state at p∼9 GPa is associated with an enhancement of T _N. At higher pressures, both TN and the transferred magnetic hyperfine field decrease, with a collapse of magnetism at ∼18.5 GPa. The results are explained by a volume-dependent competition between indirect Ruderman-Kittel-Kasuya-Yosida interaction and the 5f-ligand hybridization.