The intermetallic compounds YbAu x Ga 2 À x (0.26 r xr 1.31) were synthesized by melting of elemental components and subsequent annealing. The crystal structure of YbAu 1.04 Ga 0.96 was investigated using single-crystal X-ray diffraction data: structure type TiNiSi, space group Pnma, a= 7.1167(3) Å, b =4.5019(3) Å, c= 7.7083(3) Å, R F =0.028 for 27 variables and 441 reflections. At 600 1C this compound is described as partially substituted TiNiSi type and shows a homogeneity range around the equiatomic composition YbAu x Ga 2 À x (0.94 r xr 1.19). For the gallium-(0.26 r xr 0.83) and gold-rich (1.21 r xr 1.31) regions, the KHg 2 type of crystal structure (space group Imma) with mixed Au/Ga occupation is found. A temperature-driven phase transition for the composition YbAuGa from ordered TiNiSi to disordered KHg 2 structure type is observed at 629 1C. Yb L III X-ray absorption spectra indicate an intermediate valence of +2.5 for Yb atoms in YbAuGa. For samples deviating from this composition a further reduced valence of Yb is observed. Magnetic susceptibility studies show a non-magnetic 4f 14 ground state of Yb atoms with thermal fluctuations towards the 4f 13 state.