THERMAL-CONDUCTIVITY AND THERMOELECTRIC-POWER OF UBE13

J. Physique Lett. ler L-811 - L-817 SEPTEMBRE L-811 Classification Physics Abstracts 72.15E - 72.15J - 74.30E Thermal D. conductivity and thermoelectric UBe13 Jaccard, J. Flouquet Centre de Recherches France Z. power of Fisk, sur les Tres Basses Temperatures, CNRS, BP 166 X, 38042 Grenoble Cedex, J. L. Smith Materials Science and NM 87545, U.S.A. Technology Division, Los Alamos National Laboratory, Los Alamos, and H. R. Ott Laboratorium fur Festkorperphysik, CH-8093 Zurich, Switzerland Eidgenossische Technische Hochschule, Honggerberg, (Refu le 8 avril 1985, accepte sous forme definitive le 8 juillet 1985) Des mesures de resistivite, pouvoir thermoelectrique et de conductivite thermique du compose a fermions lourds UBe13 ainsi que leurs relations avec le diagramme de phase temperature- champ critique sont presentees. A basse temperature (T 1 K), le pouvoir thermoelectrique de la phase normale est gigantesque. La conductivite thermique suit une loi en T2 dans la phase supra- conductrice sans contribution lineaire en T contrairement a ce qui est observe dans UPt3. Resume. Measurements of the resistivity, thermoelectric power and thermal conductivity of the heavy fermion compound UBe13 and their relations to the temperature-upper critical field phase diagram are reported. At low temperature (T 1 K), enormous thermoelectric powers are detected in the normal phase. The thermal conductivity obeys a T2 law in the superconducting phase with no supplementary T contribution which is not observed in the other heavy fermion compound UPt3. Abstract 1. Introduction. The discovery of superconductivity in UBe 13 at T~ ~ 0.9 K [1] has revived the debate on the origin of the superconductivity in heavy fermion compounds first found in CeCu2 Si2 [2]. The heavy fermion character of UBel3 is proved by the large value of the ratio of the specific heat C to the temperature T near Tc : Cl T - 1 J/mole/K2 [3]. One of the peculiarities of UBe 13 is that the elec- tron mean free path is extremely short near T~. At 1 K, the electrical resistivity ( p ~ 190 Jl!} cm) [ 1-4] is almost that estimated for the unitary limit; no sign of Fermi liquid behaviour ( p ~ T 2) is detected By contrast with liquid 3 He for which the superfluid transition ( T~ ~ 2 mK) is far below the Fermi temperature TF [5], the definition of TF is not obvious. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyslet:019850046017081100