Gap formation in the semimetal U₂Ru₂Sn: Evidence from¹¹⁹Sn NMR investigations

We report measurements of the ¹¹⁹Sn nuclear spin-lattice relaxation rate 1/T₁ and the Knight shift K for polycrystalline U₂Ru₂Sn powder samples as a function of temperature. The T dependence of 1/T₁ is very similar to that of CeNiSn with the only difference that the temperature scale is increased roughly by a factor of 10. Therefore a first estimate gives a (pseudo-) gap value of Δ/k_B ≈ 140 K (≈ 14 K for CeNiSn). At low temperatures similar to CeNiSn a T₁ T = constant behaviour is observed which indicates the presence of a residual density of states at the Fermi level N(E_F) in the pseudo-gap. Knight shift measurements on oriented polycrystalline powder samples show nearly no magnetic anisotropy, whereas the temperature dependence roughly follows the behaviour of the magnetic susceptibility. First investigations on the non-magnetic reference compound Th₂Ru ₂Sn are also discussed.