E. Todorov et Sc. Sevov, DELTAHEDRAL CLUSTERS IN NEAT SOLIDS - SYNTHESIS AND STRUCTURE OF THE ZINTL PHASE CS4PB9 WITH DISCRETE PB-9(4-) CLUSTERS, Inorganic chemistry, 37(15), 1998, pp. 3889
Isolated clusters of Pb-9(4-) with the shape of monocapped square anti
prisms are found in Cs4Pb9 made by direct fusion of the elements. A ''
close-packed'' layer of clusters viewed along c of the monoclinic cell
is shown to the right (b is vertical).