Phase relations were established in the Sr-poor part of the ternary systems Sr-Ni-Si (900 1C) and Sr-Cu-Si (800 1C) by light optical microscopy, electron probe microanalysis and X-ray diffraction on as cast and annealed alloys. Two new ternary compounds SrNiSi 3 (BaNiSn 3 -type) and SrNi 9 À x Si 4 + x (own-type) were found in the Sr-Ni-Si system along with previously reported Sr(Ni x Si 1 À x ) 2 (AlB 2 -type). The crystal structure of SrNi 9 À x Si 4 + x (own-type, x= 2.7, a= 0.78998(3), c= 1.1337(2) nm; space group P4/nbm) was determined from X-ray single crystal counter to be a low symmetry derivative of the cubic, parent NaZn 13 -type. At higher Si-content X-ray Rietveld refinements reveal the formation of a vacant site (&) corresponding to a formula SrNi 5.5 Si 6.5 & 1.0 . Phase equilibria in the Sr-Cu-Si system are characterized by the compounds SrCu 2 À x Si 2 + x (ThCr 2 Si 2 -type), Sr(Cu x Si 1 À x ) 2 (AlB 2 -type), SrCu 9 À x Si 4 + x (0r xr 1.0; CeNi 8.5 Si 4.5 -type) and SrCu 13 À x Si x (4 r xr 1.8; NaZn 13 -type). The latter two structure types appear within a continuous solid solution. Neither a type-I nor a type-IX clathrate compound was encountered in the Sr-{Cu,Ni}-Si systems.
Structural details are furthermore given for about 14 new ternary compounds from related alloy systems with Ba.