Powder sintering reactions of the elements or of appropriate binary phases in welded (\mathrm{Ta}) containers have resulted in the single phase syntheses of (17 \mathrm{La}{5} \mathrm{~Pb}{3} Z) derivatives of (\mathrm{La}{5} \mathrm{~Pb}{3}) with stuffed (\mathrm{Mn}{5} \mathrm{Si}{3})-type structures (\left(P 6_{3} / m c m\right)), namely, (Z=B_{x}, \mathrm{C}{x}, \mathrm{P}, \mathrm{S}, \mathrm{Cl}), (\mathrm{As}, \mathrm{Se}, \mathrm{Sb}, \mathrm{Cr}, \mathrm{Mn}, \mathrm{Fe}, \mathrm{Co}, \mathrm{Ni}, \mathrm{Cu}, \mathrm{Zn}, \mathrm{Ru}), and (\mathrm{Ag} \cdot(\mathrm{Z}=\mathrm{N}), (O) form a (\mathrm{Cr}{5} \mathrm{~B}{3})-type derivative.) Possible (x) values for (\mathrm{B}) and (\mathrm{C}) are consistent with, but not proof of, Zintl phase characteristics. (\mathrm{La}{5} \mathrm{~Pb}{3}) was shown to be a line phase, while the reported binary (\mathrm{La}{4} \mathrm{P}{3}\left(\right.) anti- (\mathrm{Th}{3} \mathrm{P}{4}) ) was not found. The volume changes observed on incorporation of (Z) into (\mathrm{La}{3} \mathrm{~Pb}_{3}) are the smallest found in this sort of system except for chloride in the even more weakly bound alkaline-earth-metal-pnictide analogues. O 1994 Academic Press, Inc.