Superconductivity in Y7 R u4InG e12

We report a type-II intermetallic superconductor Y7Ru4InGe12 with a transition temperature (Tc) of ∼5.8 K, which is confirmed by zero resistivity, diamagnetic magnetic susceptibility, and specific-heat jump. Single crystals of Y7Ru4InGe12 were grown from a reactive indium flux. Y7Ru4InGe12 crystallizes in the tetragonal space group P4/m and features a [Ru4InGe12] polyanionic network with Y atoms located in three different channels. The upper critical fields of Y7Ru4InGe12 at 0 K are determined to be ∼5.3 and 2.4 T along the c axis and the ab plane, respectively. The estimated coherence length along the c axis (∼174 Å) is much larger than the estimated mean free path along the c axis (∼29 Å) in Y7Ru4InGe12, placing its superconductivity in the so-called dirty regime. The compound exhibits a large superconducting specific-heat jump ΔCγeTc≈2.4, significantly well above the weak-coupling Barden-Cooper-Schrieffer theoretical value of 1.43 and pointing to a strong-coupling scenario in Y7Ru4InGe12. Density-functional-theory calculations show that the density of states in Y7Ru4InGe12 exhibits a broad peak near the Fermi level which mainly derives from Y-4d,Ru-4d, and Ge-4p states.