Zr5Sb3-first Superconductor in the Mn5Si3-type system

Systematic exploration for superconductivity in the Zr₅X₃ (x =Sb, Sn, Ge, Ga, and Al) system have been carried out, and we report the discovery of superconductivity at 2.3 K in Zr₅Sb₃, the first superconducting member in the large compound family of the Mn₅Si₃-structure type. Transport, magnetic, and calorimetric measurements clearly demonstrate the bulk superconductivity for the Zr₅Sb₃ and band structure calculations suggest it to be a possible phonon-mediated BCS superconductor, with a relatively large density of states at the Fermi level associated with the d-electrons of Zr and substantially larger electron-phonon coupling compared to the Sn counterpart compound Zr₅Sn₃. Detailed doping studies have shown that superconductivity in Zr₅Sb₃ is rather robust with Hf- and Y-substitution of Zr, but suppressed by Ti-substitution. It is also suppressed by interstitial filling in Zr₅Sb₃Z by Z = Sb, C, or O.