Probing the superconductivity of PrPt4Ge12 through Ce substitution
  We report measurements of electrical resistivity, magnetic susceptibility, specific heat, and thermoelectric power on the system Pr1-xCexPt4Ge12. Superconductivity is suppressed with increasing Ce concentration up to x = 0.5, above which there is no evidence for superconductivity down to 1.1 K. The Sommerfeld coefficient {\gamma} increases with increasing x from 48 mJ/mol K^2 up to 120 mJ/mol K^2 at x = 0.5, indicating an increase in strength of electronic correlations. The temperature dependence of the specific heat at low temperatures evolves from roughly T^3 for x = 0 to e^(-\Delta /T) behavior for x = 0.05 and above, suggesting a crossover from a nodal to a nodeless superconducting energy gap or a transition from multiband to single-band superconductivity. Fermi-liquid behavior is observed throughout the series in low-temperature magnetization, specific heat, and electrical resistivity measurements. 
K. Huang, L. Shu, I. K. Lum, B. D. White, M. Janoschek, D. Yazici, J.   J. Hamlin, D. A. Zocco, P.-C. Ho, R. E. Baumbach, an...
cond-mat.str-el cond-mat.supr-con