The introduction of alkali metals into reactions expands the variety of quaternary compounds with discrete rare-earth-metal clusters centered by transition metals and yields compounds with more open structure frameworks. The larger transition-metal interstitials Co or Os appear largely responsible for a different linkage of the R(6)I(12) cluster units into layers rather than into a three-dimensional network known for other compounds with the uncommon stoichiometry R(6)I(13)Z.