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TT: Tiefe Temperaturen

TT 16: Postersitzung II: Amorphe und Tunnelsysteme, Mesoskopische Systeme, Schwere Fermionen, Kernmagnetismus

TT 16.27: Poster

Tuesday, March 27, 2001, 14:30–17:00, Rang S\ 3

Evidence for the formation of a hybridization gap in U₂Ru₂Sn — •V.H. Tran¹, S. Paschen¹, M. Baenitz¹, A. Rabis¹, F. Steglich¹, P. de V. Du Plessis², and A.M. Strydom² — ¹Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, D-01187 Dresden, Germany — ²Department of Physics, University of the Witwatersrand, PO Wits 2050, Johannesburg, South Africa

We present magnetic susceptibility χ(T), electrical resistivity ρ(T), magnetoresistance MR(H,T), Hall coefficient R_H(H,T), thermal conductivity κ(T), and thermopower S(T) data for U₂Ru₂Sn. χ(T) exhibits a broad maximum at T_max = 165 K, typical of valence-fluctuating compounds. ρ(T) also shows a broad maximum but at a lower temperature of 125 K. This temperature concurs with a maximum in the S(T) dependence. However, below 20 K, ρ(T) exhibits an upturn, while S(T) displays a pronounced shoulder and then sharply drops. Furthermore, from the temperature dependence of the carrier number, a gap energy is estimated to be about 1.6 meV. A maximum in κ (T) is observed at 30 K, below which κ steeply decrease with decreasing temperature. These observed physical properties show many similarities to those reported for known Kondo insulators (CeNiSn, Ce₃Bi₄Pt₃, CeRhSb, SmB₆, YbB₁₂), where a hybridization gap is believed to develop in the electronic density of states. Moreover, the large and positive MR of 22 % at 2 K and in 130 kOe suggests that the center of the gap locates slightly above the Fermi energy. Further investigations which can confirm the gapped state in U₂Ru₂Sn, notably specific heat and ¹¹⁹Sn NMR, are currently under progress.