Superconducting YAu₃Si and Antiferromagnetic GdAu₃Si with an Interpenetrating Framework Structure Built from 16-Atom...

Investigations of reaction mixtures RE(Au_0.79Si_0.21)_100- (RE = Y and Gd) yielded the compounds REAu₃Si which adopt a new structure type, referred to as GdAu₃Si structure (tP80, P4₂/mnm, Z = 16, a = 12.8244(6)/12.7702(2) Å, and c = 9.0883(8)/9.0456(2) Å for GdAu₃Si/YAu₃Si, respectively). REAu₃Si was afforded as millimeter-sized faceted crystal specimens from solution growth employing melts with composition RE₁₈(Au_0.79Si_0.21)₈₂. In the GdAu₃Si structure, the Au and Si atoms are strictly ordered and form a framework built of corner-connected, Si-centered, trigonal prismatic units SiAu₆. RE atoms distribute on 3 crystallographically different sites and each attain a 16-atom coordination by 12 Au and 4 Si atoms. These 16-atom polyhedra commonly fill the space of the unit cell. The physical properties of REAu₃Si were investigated by heat capacity, electrical resistivity, and magnetometry techniques and are discussed in the light of theoretical predictions. YAu₃Si exhibits superconductivity around 1 K, whereas GdAu₃Si shows a complex magnetic ordering, likely related to frustrated antiferromagnets exhibiting chiral spin textures. GdAu₃Si-type phases with interesting magnetic and transport properties may exist in an extended range of ternary RE-Au-Si systems, similar to the compositionally adjacent cubic 1/1 approximants RE(Au,Si)_∼6.