An altered mixture of alkali metals and a trace of hydrogen afford a novel variant of bce Na4K6Tl13 in which one Tl-centered icosahedron is replaced by a regular H-centered octahedron, and the other, by a Na-centered icosahedron, the changes reflecting specific cation solvation and overall electronic requirements. The anionic polyhedral shapes and cation positions about the cell are shown on the left. Adventitious sources are sufficient to provide the hydrogen essential for the formation of this novel compound with its centered, closed-shell polyanions.