For Pt 4 Ge the as-prepared ISS intensity was 21% lower than for as-prepared Pt 4 , attributed to Ge atoms partially shadowing or blocking He + scattering from Pt. The attenuations of the Pt ISS signal, relative to as-prepared Pt 4 Ge, were 22%, 44%, and 70% after 1, 6, and 21 TPD runs respectively, similar to Pt 4 . In contrast, the loss of strong of ethylene binding sites per Pt 4 Ge was much smaller than for Pt 4 , at 5%, 24%, and 44%, respectively. Pt 4 Ge clusters were estimated to have a total of˜2 C atoms present per cluster after 6 TPDs -just one third of the number deposited per Pt 4 . Thus, experiment shows that there is less, but still significant coking on Pt 4 Ge, that similar fractions of the initial Pt atoms remain in the surface layer, and that the loss of strong ethylene binding sites is inhibited by Ge. This, too, supports our conclusions that Pt 4 Ge restructures upon the addition of C 2 , and that the improved stability of Pt 4 GeC 2 arises from electronic effects due to the interaction between the Ge, Pt, and C.