Synthesis, phase relationship and crystal structure of the new binary compound Ir13Al45

The new phase Ir13Al45 was synthesized in equilibrium with an aluminum-rich melt. Its crystal structure was established from single-crystal diffraction data. The compound crystallizes in the space group Pnma and represents a novel structure type (Pearson symbol image, a=16.760(2) Å, b=12.321(1) Å, c=17.425(2) Å). The structure can essentially be described as a simple hexagonal column packing of pseudopentagonal columns formed by irregular Al polyhedra centered by Ir atoms. Ir13Al45 forms peritectically at 895 °C and exists in equilibrium with the melt in a narrow temperature interval of 19 °C.