Superconductivity in an intermetallic oxide Hf3Pt4Ge2O* *Project supported by the National Key Research and Development Program of China (Grant Nos. 2016YFA0300303, 2017YFA0504703, 2017YFA0302904, and 2017YFA0303000), the National Basic Research Program of China (Grant No. 2015CB921304), the National Natural Science Foundation of China (Grant Nos. 11774391, 11774403, and 11804381), the Strategic Priority Research Program (B) of the Chinese Academy of Sciences

Abstract

Discovery of a new superconductor with distinct crystal structure and chemistry often provides great opportunity for further expanding superconductor material base, and also leads to better understanding of superconductivity mechanisms. Here, we report the discovery of superconductivity in a new intermetallic oxide Hf3Pt4Ge2O synthesized through a solid-state reaction. The Hf3Pt4Ge2O crystallizes in a cubic structure (space group Fm-3m) with a lattice constant of a = 1.241 nm, whose stoichiometry and atomic structure are determined by electron microscopy and x-ray diffraction techniques. The superconductivity at 4.1 K and type-II superconducting nature are evidenced by the electrical resistivity, magnetic susceptibility, and specific heat measurements. The intermetallic oxide Hf3Pt4Ge2O system demonstrates an intriguing structural feature that foreign oxygen atoms can be accommodated in the interstitial sites of the ternary intermetallic framework. We also successfully synthesized a series of Hf3Pt4Ge2O1 + δ (–0.25 ≤ δ ≤ 0.5), and found the δ-dependent superconducting transition temperature T c. The atomic structure and the electronic structure are also substantiated by first-principles calculations. Our results present an entirely new family of superconductors with distinct structural and chemical characteristics, and could attract research interest in further finding new superconductors and exploring novel physics pertaining to the 5d-electron in these intermetallic compound systems.