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We report experimental and theoretical investigations of the Hall effect in YbRh2 Si2 and its reference compounds LuRh2 Si2 and YbIr2 Si2. Based on band-structure calculations we identify two bands dominating the Hall coefficient in all these compounds. For the case of LuRh2 Si2 -the nonmagnetic reference compound of YbRh2 Si2 -the temperature dependence of the Hall coefficient is described quantitatively to arise from two holelike bands. For YbIr2 Si2 and YbRh2 Si2, renormalized band calculations yield two bands of opposite character. In YbRh2 Si2 these two bands almost compensate each other. We present strong indications that sample dependences of the low-temperature Hall coefficient observed for YbRh2 Si2 arise from slight variations in the relative scattering rates of the two bands. Minute changes in the composition appear to be the origin. The results of our band-structure calculations reveal that a transition of the 4f electrons from localized to itinerant leads to a decrease in the Hall coefficient. © 2010 The American Physical Society.

The stannide family of materials A3T4Sn13 (A=La,Sr,Ca; T=Ir,Rh) is interesting due to the interplay between a tunable lattice instability and phonon-mediated superconductivity with Tc~5-7K. In Sr3Ir4Sn13, a structural transition temperature T*~147K associated with this instability has been reported, which is believed to result from a superlattice distortion of the high-temperature phase on cooling. Here we report an experimental study of the electronic structure of a member of this material family, Sr3Ir4Sn13, through measurements of quantum oscillations and comparison with density functional theory calculations. Our measurements reveal good agreement with theory using the lattice parameters consistent with a body-centered-cubic lattice of symmetry I43d of the low-temperature phase. The study of the fermiology of Sr3Ir4Sn13 that we present here should help inform models of multiband superconductivity in the superconducting stannides. [ABSTRACT FROM AUTHOR]