Gap formation in the semimetal U2Ru2Sn: evidence from 119Sn 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/kB∼140 K (∼14 K for CeNiSn). At low temperatures similar to CeNiSn a T1T=constant behaviour is observed which indicates the presence of a residual density of states at the Fermi level N(EF) 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 Th2Ru2Sn are also discussed