SrPdGa3 - An orthorhombic superstructure of the ThCr2Si2 type

The gallide SrPdGa3 was synthesized by melting of the elements in a sealed tantalum tube in an induction furnace. SrPdGa3 crystallizes with a new structure type which was determined on the basis of single-crystal X-ray diffractometer data: Cmcm, a = 643.7(1), b = 1044.9(2), c = 600.4(1) pm, wR = 0.0283, 504 F-2 values, 19 variables. SrPdGa3 is a new ternary ordering variant of the aristotype BaAl4/ThCr2Si2. The structural relation with ThCr2Si2 and the closely related silicide BaNi2Si2 is discussed on the basis of a group-subgroup relation. The three-dimensional [PdGa3](delta-) network is dominated by Pd-Ga and Ga-Ga bonding interactions with 251-256 pm Pd-Ga and 267 pm Ga-Ga distances.