TERNARY PHASES CAPTSI, EUPTSI, SRPTSI, BAPTSI WITH THE LALRSI-TYPE STRUCTURE

Four ternary phases MPtSi (M equals Ca, En, Sr, Ba) have been shown to crystallize in the LaIrSi-type structure (space group P2//13). This ternary structure is a derivative structure of the binary SrSi//2-type structure (space group P4//332 or P4//132). In the MPtSi series the LaIrSi-type structure has a stability range for metals with radii from r//C//a equals 1. 973 Angstrom to r//B//a equals 2. 243 A in contrast to MSi//2 compounds which exist with the SrSi//2-type structure only from r//S//r equals 2. 151 A to r//B//a 2. 243 A. From a single-crystal investigation on CaPtSi remarkably short Pt-Si distances of 2. 30 A (3x) are obtained. Structural relations are discussed.