Intermediate‐Valence Intermetallic Phase YbIn 1–x Au 1+x (x = 0‐0.3) †

Polycrystalline samples YbIn 1–x Au 1+x were prepared by reaction of the elements in sealed tantalum tubes at 1170 K with a subsequent annealing at 770 K. The crystal structures of YbInAu (space group P 6; − 2 m , a = 7.6992(8), c = 4.0333(5) Å, wR 2 = 0.035, 282 reflections and 14 variables) and YbIn 0.73 Au 1.27 ( P 6; − 2 m , a = 7.706(3), c = 4.011(1) pm, wR 2 = 0.035, 275 reflections, 14 parameters) were refined from single crystal X‐ray diffraction data. The phase YbIn 1–x Au 1+x has a homogeneity range for 0.0≤x≤0.3 (770 K). The crystal structure of YbInAu contains two gold atoms located in tricapped trigonal prisms [Au1Yb 6 In 3 ] and [Au2In 6 Yb 3 ]. The indium position shows mixed occupancy by indium and gold. The main atomic interaction is the ionic one between the ytterbium (charge +1.1 is obtained from the analysis of the electron density within the quantum theory of atoms in molecules) and gold (−1.2 and −1.3) supported by the dative bonding Au→Yb. The effective charge of indium is +0.2. Magnetic susceptibility data indicate intermediate valence for Yb increasing with increasing x . The 197 Au Mössbauer spectra show a superposition of the signals for Au1 ( δ = 3.31 mm s –1 ), Au2 ( δ = 5.37 mm s –1 ), and Au(In) indicating auridic character of gold.