The delayed ionization behavior of several single and binary transition metal-carbon cluster systems, in which metallocarbohedrenes (Met-Cars) are produced, is reported. The single metal Met-Cars, M8C12, where M=Ti, Nb, or Zr, and the binary metal Met-Cars, TixMyC12, where M=Zr, Nb, or Ta and x+y = 8, are investigated at various selected photoionization wavelengths (266, 355, 532, 590, and 620 nm) and over a range of fluences (20 to 120 mJ/cm(2)). In addition, a variable temperature experiment is performed in order to estimate the initial internal energy of the clusters after expansion from a laser vaporization sourer. Delayed ionization, which is observed at all wavelengths studied, is well described by a statistical model based on an adaptation of the Richardson-Dushman relation. The new findings reported herein provide evidence that all of phase space is sampled, supporting the proposal that the observed delayed ionization is thermionic in character. The temporal dependence of the ionization is found to correlate with the ionization potentials of two systems whose values are available. The ionization potential trends of the mixed metal Met-Cars can by predicted using the thermionic emission model.