Superconductivity in the Layered Cage Compound Ba3Rh4Ge16 Supported the National Key R&D Program of China (Grant No. 2018YFA0704300), the National Natural Science Foundation of China (Grant Nos. U1932217, 11974246, and 12004252), the Natural Science Foundation of Shanghai (Grant No. 19ZR1477300), the Science and Technology Commission of Shanghai Municipality (Grant No. 19JC1413900), and the Analytical Instrumentation Center, SPST, ShanghaiTech University (Grant

Abstract

We report the synthesis and superconducting properties of a layered cage compound Ba3Rh4Ge16. Similar to Ba3Ir4Ge16, the compound is composed of 2D networks of cage units, formed by noncubic Rh–Ge building blocks, in marked contrast to the reported rattling compounds. The electrical resistivity, magnetization, specific heat capacity, and μSR measurements unveiled moderately coupled s-wave superconductivity with a critical temperature T c = 7.0 K, the upper critical field μ 0 H c2(0) ∼ 2.5 T, the electron-phonon coupling strength λ e−ph ∼ 0.80, and the Ginzburg–Landau parameter κ ∼ 7.89. The mass reduction with the substitution of Ir by Rh is believed to be responsible for the enhancement of T c and coupling between the cage and guest atoms. Our results highlight the importance of atomic weight of framework in cage compounds in controlling the λ e−ph strength and T c.