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TT: Fachverband Tiefe Temperaturen
TT 25: f-Electron Systems
TT 25.8: Talk
Tuesday, March 10, 2026, 11:30–11:45, HSZ/0101
Yb5Rh6Sn18: a valence fluctuating system with ultra-low thermal conductivity — •Oleksandr Bolielyi1, Volodymyr Levytskyi1, Kristina O. Kvashnina2, Andreas Leithe-Jasper3, and Roman Gumeniuk1 — 1Institut für Experimentelle Physik, TU Bergakademie Freiberg, 09596 Freiberg, Germany — 2Helmholtz-Zentrum Dresden-Rossendorf (HZDR), 01314 Dresden, Germany — 3Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
Yb5Rh6Sn18 obtained by high-frequency melting of elemental metals crystallizes with an unique structural configuration closely related to the Yb3Rh4Sn13 Remeika prototype. An important feature of this structure is that the small Sn1-atoms reside within enlarged Frank-Kasper polyhedra thus, possessing potential for a "rattling" motion. X-ray absorption spectra of Yb5Rh6Sn18 indicate Yb-ions to be in the intermediate valence state (IVS), i.e. switching between the 4f13 (Yb3+) and 4f14 (Yb2+) configurations. In agreement with this finding temperature dependence of magnetic susceptibility reveals a well pronounced maximum. Both Hall and Seebeck coefficients indicate the change of charge carrier type from electrons to holes between 120 and 220 K. Together with electrical resistivity and theoretical DFT calculations these effects confirm Yb5Rh6Sn18 to be a metal, which disobeys the free electron gas theory. The ultra-low thermal conductivity is attributed to the appearance of phonon resonance as well as to the "rattling" motion of Sn1 atoms in the studied structure.
Keywords: magnetism; valence fluctuations; thermal transport; crystal structure