Specific heat of amorphous Ce_xRu_100-x alloys

We have measured the specific heat on sputtered amorphous (a-) Ce_xRu_100-x alloys for 15≤ x≤80 from 5 to 300 K. The C_p/T nicely follows a function of γ+BT² above 8 K in each Ce concentration. In the Ce-rich side (x≥67), the electronic specific coefficient γ shows a very large value (γ=180 mJ/mol K² at x=80), suggesting formation of the heavy fermion (dense Kondo) state at low temperature. However, the γ decreases rapidly with decreasing the Ce concentration. In the Ru-rich side (x<39), the γ becomes less than 10 mJ/mol K² and the superconductivity occurs. This γ-value is almost the same as for a-Ce_20-yLa_yRu₈₀ in each La concentration, where the superconductivity occurs at the same superconducting temperature T_c. We made the Kadowaki-Woods plot from the coefficient A of the T² term in resistivity and γ in the Ce-rich side. The value of A/γ² for present alloys shows about 3.5×10^-6 μ Ω cm(mol K²/mJ)².