Intermediate-valence behavior in U2Rh2Sb

D. Legut; M. Krnel; P. Koželj; Yu. Prots; M. Juckel; U. Burkhardt; A. Ormeci; Yu. Grin; A. Leithe-Jasper; J. Kolorenč; E. Svanidze; U. D. Wdowik

doi:10.1016/j.jnucmat.2026.156829

arXiv · 2507.10720

Intermediate-valence behavior in U2Rh2Sb

D. Legut·M. Krnel·P. Koželj·Yu. Prots·M. Juckel·U. Burkhardt·A. Ormeci·Yu. Grin·A. Leithe-Jasper·J. Kolorenč·E. Svanidze·U. D. Wdowik

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Abstract

Intermediate-valence behavior is sometimes observed in lanthanide-based materials containing Ce, Yb, Sm or Eu. However, the number of actinide-based systems that exhibit this type of behavior is rather limited. In this work, we present the discovery and characterization of a uranium compound U2Rh2Sb, which turns out to be a candidate for the intermediate-valencebehavior. The material shows a characteristic feature in the magnetic susceptibility around T = 50 K, which can be described within the interconfiguration-fluctuation model of intermediate valence systems. We find the energy difference between the 5f3(U3+) and 5f2(U4+) states to be $\delta$Eex/kB $\approx$ 400 K and the corresponding valence fluctuation temperature to be Tvf $\approx$ 140 K. The value of the electronic specific heat coefficient $\gamma$ = 50 mJ mol-1 U K-2 signals a modest electron effective mass enhancement. The electrical resistivity indicates metallic behavior, albeit with a small residual resistivity ratio. Measurements of thermoelectric properties indicate a change of sign in the Seebeck coefficient around T = 100 K, with a minimum achieved at T = 50 K, which coincides with the broad peak observed in magnetic susceptibility. The experimental results are compared with the theoretical analysis, based on the first-principles calculations, including lattice dynamics.

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D. Legut, M. Krnel, P. Koželj, Yu. Prots, M. Juckel, U. Burkhardt, A. Ormeci, Yu. Grin, A. Leithe-Jasper, J. Kolorenč, E. Svanidze, U. D. Wdowik. 2025-07-14. Intermediate-valence behavior in U2Rh2Sb. https://doi.org/10.1016/j.jnucmat.2026.156829

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