Uranium cobalt tetraaluminide, UCoAl4.
The structure of UCoAl(4) can be viewed as a succession of atomic layers, with the compositions UCoAl and Al(3), that alternate along the c axis. The packing within the pure Al layer at z = 1/2 results from edge-sharing of triangles, squares and pentagons of Al atoms. Two successive Al(3) layers thus define pentagonal, square-based and trigonal prisms which are centred at z = 0 by the U, Co and remaining Al atoms. UCoAl(4) is a high-temperature phase that is only observed in as-cast samples.
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