Gold-rich R3Au7Sn3: establishing the interdependence between electronic features and physical properties

Two new polar intermetallic compounds Y3Au7Sn3 (I) and Gd3Au7Sn3 (II) have been synthesized and their\udstructures have been determined by single crystal X-ray diffraction (P63/m; Z = 2, a = 8.148(1)/8.185(3),\udand c = 9.394(2)/9.415(3) for I/II, respectively). They can formally be assigned to the Cu10Sn3 type\udand consist of parallel slabs of Sn centered, edge-sharing trigonal Au6 antiprisms connected through\udR3 (R = Y, Gd) triangles. Additional Au atoms reside in the centres of trigonal Au6 prisms forming\udAu@Au6 clusters with Au–Au distances of 2.906–2.960 Å, while the R–R contacts in the R3 groups are\udconsiderably larger than the sums of their metallic radii. These exclusive structural arrangements provide\udalluring systems to study the synergism between strongly correlated systems, particularly, those in the\udstructure of (II), and extensive polar intermetallic contacts, which has been inspected by measurements\udof the magnetic properties, heat capacities and electrical conductivities of both compounds. Gd3Au7Sn3\udshows an antiferromagnetic ordering at 13 K, while Y3Au7Sn3 is a Pauli paramagnet and a downward\udcurvature in its electrical resistivity at about 1.9 K points to a superconducting transition. DFT-based\udband structure calculations on R3Au7Sn3 (R = Y, Gd) account for the results of the conductivity measurements\udand different spin ordering models of (II) provide conclusive hints about its magnetic structure.\udChemical bonding analyses of both compounds indicate that the vast majority of bonding originates\udfrom the heteroatomic Au–Gd and Au–Sn interactions, while homoatomic Au–Au bonding is evident\udwithin the Au@Au6 cluster