Towards strongly correlated semimetals: U2Ru2Sn and Eu8Ga16Ge30 Original Research Article

We present results of transport, magnetic, and calorimetric measurements on two f-electron based compounds: U2Ru2Sn and Eu8Ga16Ge30. We show that U2Ru2Sn shares several properties with the strongly correlated semimetal CeNiSn. These analogies suggest that in U2Ru2Sn a narrow energy gap (or pseudogap) opens which is one order of magnitude larger than the one of CeNiSn. The two modifications of the clathrate Eu8Ga16Ge30 behave as local-moment ferromagnetic metals with relatively low Curie temperatures and small charge-carrier concentrations. The thermal conductivity is low and glass-like, as expected for ‘filled-cage’ systems. If, by modification of the Ga–Ge cages, a ‘Kondo insulating’ ground state could be realized, a high thermoelectric figure of merit associated with the (pseudo)gap opening would be expected.