We have used photoionization efficiency spectroscopy to determine ionization energies (IEs) of the gas-phase tantalum-carbide Clusters Ta5Cy (y = 0-6). The structures of the Clusters observed ill the experiment are assigned by comparing the experimental IEs with those of candidate isomers, calculated by density Functional theory. Two competing geometries of the Underlying Ta-5, cluster are found to be present in the assigned Ta5Cy Structures; either a "prolate" or "distorted oblate" trigonal bipyramid geometry. The onset of carbon-carbon bonding in the Ta5Cy series is proposed to occur at y = 6, with lie structure of Ta5Cy containing two molecular C-2 units.