Intermediate-Valence Ytterbium Compound Yb₄Ga₂₄Pt₉: Synthesis, Crystal Structure, and Physical Properties

The title compound was synthesized by a reaction of the elemental educts in a corundum crucible at 1200 °C under an Ar atmosphere. The excess of Ga used in the initial mixture served as a flux for the subsequent crystal growth at 600 °C. The crystal structure of Yb₄Ga₂₄Pt₉ was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group <i>C</i>2<i>/m</i>, Pearson symbol <i>mS</i>74, <i>a</i> = 7.4809(1) Å, <i>b</i> = 12.9546(2) Å, <i>c</i> = 13.2479(2) Å, β = 100.879(1)°, <i>V</i> = 1260.82(6) ų, <i>R</i>_<i>F</i> = 0.039 for 1781 observed reflections and 107 variable parameters. The structure is described as an <i>ABABB</i> stacking of two slabs with trigonal symmetry and compositions Yb₄Ga₆ (<i>A</i>) and Ga₁₂Pt₆ (<i>B</i>). The hard X-ray photoelectron spectrum (HAXPES) of Yb₄Ga₂₄Pt₉ shows both Yb²⁺ and Yb³⁺ contributions as evidence of an intermediate valence state of ytterbium. The evaluated Yb valence of ∼2.5 is in good agreement with the results obtained from the magnetic susceptibility measurements. The compound is a bad metallic conductor