Dense Kondo behavior in the low-temperature resistivity and specific heat for amorphous Ce₅₀Al₅₀ alloy

We measured the low-temperature specific heat C_p, resistivity ρ, and magnetoresistance Δρ(H)/ρ(0) for amorphous Ce₅₀Al₅₀ synthesized by a DC high-rate sputter method. The low-temperature C_p (T < 2 K) decreases rapidly toward 0 K and has no indication of phase transition. The value of γ₀ which is extrapolated down to 0 K of the C_p/T is 117 mJ/molK². The temperature dependence of ρ increases with decreasing temperature down to 0.6 K. We found that both a weak localization effect and a coherent Kondo state might be realized in the low-temperature region for the present alloy from the conductivity analysis. Furthermore, in the low-temperature ρ, a T² term with a very large coefficient A was observed. The ratio of A/γ₀ ² is 0.63 ×10^-5 (μΩcm/K²)/(mJ/molK²)² and is near the value of typical Ce-based heavy-fermion compounds. The magnetoresistances Δρ(H)/ρ(0) at 0.5 K and 2 K are almost constant in the magnetic field region of H < 10 kOe. We considered that the negative magnetoresistance effect is due to the weak localization and the positive magnetoresistance to the heavy-fermion state in the present alloy.