Intermediate‐Valence Intermetallic Phase YbIn1–xAu1+x (x = 0‐0.3)

Polycrystalline samples YbIn1–xAu1+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 P6;−2m, a = 7.6992(8), c = 4.0333(5) Å, wR2 = 0.035, 282 reflections and 14 variables) and YbIn0.73Au1.27 (P6;−2m, a = 7.706(3), c = 4.011(1) pm, wR2 = 0.035, 275 reflections, 14 parameters) were refined from single crystal X‐ray diffraction data. The phase YbIn1–xAu1+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 [Au1Yb6In3] and [Au2In6Yb3]. 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 197Au 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. The phase YbIn1–xAu1+x has a homogeneity range for 0.0 ≤ x ≤0.3 (770 K). Ionic interaction between the ytterbium and gold is supported by the dative bonding Au→Yb. Intermediate valence for Yb increases with increasing x. The 197Au Mössbauer spectra show a superposition of the signals for Au1 (δ = 3.31 mm s–1) and Au2 (δ = 5.37 mm s–1), indicating auridic character of gold.