The title compound was synthesized in a niobium container by fusion of the elements followed by slow cooling. In the first stage, the stoichiometric proportion KNaCd3Tl7 yielded a heterogeneous product containing a few single crystals of the compound K-6(Na-2.36(9)Cd-1.64(9))Tl12Cd, the structure of which was established by a single crystal X-ray diffraction technique (cubic, Im(3) over bar, a = 11.352(2) Angstrom, Z = 2, R(F) = 3.24%, Rw(F) = 4.60%). Occurrence of a stoichiometry range for the compound was indicated after a new reaction starting from the composition K6Na2Cd3Tl12 gave a quite homogeneous and well-crystallized product (refined composition K-6(Na-1.93(7)Cd-2.07(7))Tl12Cd, Im(3) over bar, a = 11.321(2) Angstrom, Z = 2, R(F) = 3.98%, Rw(F) = 4.99%). The structure of K-6(NaCd)(2)Tl12Cd is distinguishable from that reported for Na4K6Tl13 by replacement of the icosahedron centering thallium and of half the sodium cations by cadmium. Statistical occupation disorder occurs on the 8(c) position of the outer Cd/Na atom. The structure contains the 50-electron closed shell centered Tl12Cd12- icosahedral cluster with <(3)over bar m> symmetry (T-h) Extended Huckel molecular orbital and band calculations were carried out to analyze the centering effect on the anion stability and look at the electron transfer, especially from cadmium lying within the first coordination shell of the icosahedral cluster. Electron localization within the Cd-centered icosahedron is not as evident as in the Tl-centered thallium icosahedral clusters described elsewhere; actually, cadmium is found to bridge icosahedra within a more three-dimensional network than sodium by forming bonds that are mainly covalent. The compound is a semiconducting Zintl phase with closed shell bonding.