The Solid Solution Mg x In 3—x Ir — Formation of the FeGa 3 Type up to x = 0.73 and the Cementite Structure with x = 0.92

Various compounds within the solid solution Mg x In 3—x Ir ( x = 0—0.92) have been prepared from the elements by melting in glassy carbon crucibles in a water‐cooled sample chamber in a high‐frequency furnace. The structures of six single crystals with x = 0.25, 0.58, 0.62, 0.64, 0.71, and 0.73 have been refined from X‐ray diffractometer data. These intermetallics crystallize with the tetragonal FeGa 3 structure, space group P 4 2 / mnm : a = 700.6(1), c = 709.1(1) pm, w R2 = 0.0397, 296 F 2 values, 18 parameters for Mg 0.73 In 2.27 Ir. This structure is an intergrowth of AlB 2 and >W related slabs. The 4 c and 8 j indium sites show mixed occupancy with magnesium. For all crystals the 4 c site within the cubes has a higher magnesium population. With increasing magnesium content, a switch in the structure type is observed. Mg 0.92 In 2.08 Ir adopts the Fe 3 C structure, space group Pnma : a = 745.5(3), b = 837.7(3), c = 514.2(2) pm, w R2 = 0.0724, 738 F 2 values, 25 parameters. The iridium atoms are coordinated by eight (FeGa 3 type) and nine (Fe 3 C type) indium/magnesium atoms in both structure types. The FeGa 3 and the Fe 3 C type both derive from the aristotype U 3 Si 2 as presented by a group‐subgroup scheme.