Neodymium rhodium aluminide NdRh4Al15.37

The new compound NdRh4Al15.37 has been prepared by reaction of the elemental components with an excess of aluminium at high temperature and cooling at a slow rate. It crystallizes with the tetragonal space group P42/nmc, a=912.4(1) pm, c=1561.6(3) pm, Z=4. The structure was determined using four-circle diffractometer data and refined to R=0.030 for 934 structure factors and 63 variable parameters. The atoms occupy twelve atomic sites, all with high coordination numbers. Four of the nine aluminium positions are very close to each other. They form a nearly straight row with partial occupancy. Similar to other structures of intermetallics with a high content of aluminium, the structure can be partitioned into layers of two types. One is hexagonally close packed and puckered and consists only of transition metal (Rh) and aluminium atoms. The other type of layer is less densely packed and contains, besides (mainly) aluminium and rhodium, all of the neodymium atoms. (orig.)