Intermediate-Valence Ytterbium Compound Yb 4 Ga 24 Pt 9 : 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 Yb ₄ Ga ₂₄ Pt ₉ was determined from single-crystal X-ray diffraction data: new prototype of crystal structure, space group C2/m, Pearson symbol mS74, a = 7.4809(1) Å, b = 12.9546(2) Å, c = 13.2479(2) Å, β = 100.879(1)°, V = 1260.82(6) Å ³ , R _F = 0.039 for 1781 observed reflections and 107 variable parameters. The structure is described as an ABABB stacking of two slabs with trigonal symmetry and compositions Yb ₄ Ga ₆ (A) and Ga ₁₂ Pt ₆ (B). The hard X-ray photoelectron spectrum (HAXPES) of Yb ₄ Ga ₂₄ Pt ₉ shows both Yb ²⁺ and Yb ³⁺ 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.