A mixed carbon-metal cluster is designed by combining the tetrahedral C₅ radical (with a central atom—the skeleton of the C₅H₁₂ molecule) and the spherical Au₁₂ layer (the external atomic shell of the Au₁₃ cluster). The C₅Au₁₂ cluster and its negative and positive ionic derivatives, C₅Au₁₂^±, are investigated ab initio (DFT) in terms of optimized structures and relative energies of a few spin-states, for the icosahedral-like and octahedral-like isomers. The cluster is predicted to be generally more stable in its octahedral shape (similar to C₅H₁₂) which prevails for the negative ion and may compete with the icosahedral shape for the neutral system and positive ion. Adiabatic ionization energies (AIE) and electron affinities (AEA) of C₅Au₁₂, vertical electron-detachment (VDE) energies of C₅Au₁₂⁻, and vertical ionization and electron-attachment energies (VIE, VEA) of C₅Au₁₂ are calculated as well, and compared with those for the corresponding isomers of the Au₁₃ cluster. The AIE and VIE values are found to be close for the two systems, while the AEA and VDE values are significantly reduced for the radical-based species. A simple fragment-based model is proposed for the decomposition of the total interaction into carbon–gold and gold–gold components.