Cover illustration: A displacement ellipsoid plot, showing the atomic numbering scheme of sodium rubidium sodium (+)-tartrate tetrahydrate. Ellipsoids are drawn at the 50% probability level and H atoms are drawn as spheres with arbitrary radii. See Lutz & Schreurs [Acta Cryst. (2008), C64, m296-m299].
Li12Cu16+xAl26−x (x = 3.2) is a new intermetallic structure type that is related to the CaCu5, LiCuAl2 and Li8Cu12+xAl6−x structures because of the presence of hexagonal channels and pseudo-Frank–Kasper polyhedra packing.
UCu0.60(4)Sb2 crystallizes in the tetragonal space group P4/nmm. From this and previous studies of UCuxSb2, it is found that the a axis is invariant to x but that a linear relation holds between x and the length of the c axis for x between 0 and 1.