Composition dependent polymorphism and superconductivity in Y3+x{Rh,Ir}4Ge13-x.

Polymorphism is observed in the Y3+xRh4Ge13-x series. The decrease of Y-content leads to the transformation of the primitive cubic Y3.6Rh4Ge12.4 [x = 0.6, space group Pm3̄n, a = 8.96095(9) Å], revealing a strongly disordered structure of the Yb3Rh4Sn13 Remeika prototype, into a body-centred cubic structure [La3Rh4Sn13 structure type, space group I4132, a = 17.90876(6) Å] for x = 0.4 and further into a tetragonal arrangement (Lu3Ir4Ge13 structure type, space group I41/amd, a = 17.86453(4) Å, a = 17.91076(6) Å) for the stoichiometric (i.e. x = 0) Y3Rh4Ge13. Analogous symmetry lowering is found within the Y3+xIr4Ge13-x series, where the compound with Y-content x = 0.6 is crystallizing with La3Rh4Sn13 structure type [a = 17.90833(8) Å] and the stoichiometric Y3Ir4Ge13 is isostructural with the Rh-analogue [a = 17.89411(9) Å, a = 17.9353(1) Å]. The structural relationships of these derivatives of the Remeika prototype are discussed. Compounds from the Y3+xRh4Ge13-x series are found to be weakly-coupled BCS-like superconductors with Tc = 1.25, 0.43 and 0.6, for x = 0.6, 0.4 and 0, respectively. They also reveal low thermal conductivity (<1.5 W K-1 m-1 in the temperature range 1.8-350 K) and small Seebeck coefficients. The latter are common for metallic systems. Y3Rh4Ge13 undergoes a first-order phase transition at Tf = 177 K, with signatures compatible to a charge density wave scenario. The electronic structure calculations confirm the instability of the idealized Yb3Rh4Sn13-like structural arrangements for Y3Rh4Ge13 and Y3Ir4Ge13.

[1]  A. Salamat,et al.  Room-temperature superconductivity in a carbonaceous sulfur hydride , 2020, Nature.

[2]  R. D. Dos Reis,et al.  Pressure effects on the structural and superconducting transitions in La3Co4Sn13 , 2018, Journal of Alloys and Compounds.

[3]  J. Chan,et al.  Superconductivity in Single Crystals of Lu3T4Ge13–x (T = Co, Rh, Os) and Y3T4Ge13–x (T = Ir, Rh, Os) , 2015 .

[4]  A. P. Drozdov,et al.  Conventional superconductivity at 190 K at high pressures , 2014, 1412.0460.

[5]  V. Petříček,et al.  Crystallographic Computing System JANA2006: General features , 2014 .

[6]  D. Johnston,et al.  Elaboration of the α-model derived from the BCS theory of superconductivity , 2013, 1304.2275.

[7]  O. Prakash,et al.  Superconductivity in a low carrier density system: A single crystal study of cubic Y3Ru4Ge13 , 2013, 1301.3326.

[8]  A. Morozkin.  Gd–Co–Ge system at 870/1070 K , 2012 .

[9]  Y. Grin,et al.  Ca3Pt(4+x)Ge(13-y) and Yb3Pt4Ge13: new derivatives of the Pr3Rh4Sn13 structure type. , 2012, Dalton transactions.

[10]  C. Uher,et al.  Thermoelectric properties of rare earth–ruthenium–germanium compounds , 2007 .

[11]  K. Itoh,et al.  Mechanism of superconductivity in the polyhedral-network compound Ba8Si46 , 2003, Nature materials.

[12]  M. Continentino.  Wilson and Kadowaki-Woods ratios in heavy fermions , 1999, cond-mat/9910306.

[13]  Andreas K. Freund,et al.  Nine-crystal multianalyzer stage for high-resolution powder diffraction between 6 keV and 40 keV , 1998, Optics & Photonics.

[14]  D. Van Dyck,et al.  A simple intuitive theory for electron diffraction , 1996 .

[15]  G. Venturini,et al.  De nouveaux isotypes de U2Co3Si5 ou Lu2Co3Si5 dans les systems R-T-Ge (R = Elements Des Terres Rares; T = Ru, Co, Rh, Ir). Supraconductivite de Y2Ir3Ge5 , 1986 .

[16]  G. Venturini,et al.  De nouvelles séries de germaniures, isotypes de Yb3Rh4Sn13 et BaNiSn3, dans les systèmes ternaires TRTGe où TR est un élément des terres rares et T ≡ Co, Rh, Ir, Ru, Os , 1985 .

[17]  G. Venturini,et al.  Vingt nouveaux germaniures ternaires TR5T4Ge10 de metaux tr des terres rares et T = Co, Rh, Ir. Supraconductivite de Lu5Rh4Ge10 et Lu5Ir4Ge10 , 1984 .

[18]  J. P. Remeika,et al.  The crystal structure of SnYb3Rh4Sn12, a new ternary superconducting stannide , 1980 .

[19]  J. P. Remeika,et al.  A new family of ternary intermetallic superconducting/magnetic stannides , 1980 .

[20]  Christoph Kommer,et al.  Festkörperphysik , 1976, Tutorium Physik fürs Nebenfach.

[21]  J. Wilson,et al.  Charge-density waves and superlattices in the metallic layered transition metal dichalcogenides , 1975 .

[22]  R. Dynes.  McMillan's equation and the Tc of superconductors , 1972 .

[23]  E. Hockings,et al.  Crystal structure of iridium trisilicide, IrSi3 , 1971 .

[24]  B. Chandrasekhar.  A NOTE ON THE MAXIMUM CRITICAL FIELD OF HIGH‐FIELD SUPERCONDUCTORS , 1962 .