Antiferromagnetic Kondo lattice behaviour of YbNiAl2 alloy

We report measurements on the thermal and electronic transport properties for the YbNiAl2 compound. At low temperatures, the electrical resistivity exhibits a logarithmic increase below a local minimum at 23 K, followed by a sharp decrease into the coherent/magnetically ordered state below 4.8 K. From the magnetic contribution to the specific heat (cmagcmag), a Kondo temperature TK=5TK=5 K and an entropy value of 0.8Rln2 at the transition are estimated. The extrapolation of cmagcmag/TT vs TT plot to lower temperatures gives an estimate of the electronic coefficient γ0=300γ0=300 mJ/mol K2, which classifies this compound as a moderate heavy-fermion system. The magnetoresistance shows a single impurity Kondo scaling, with a single-ion characteristic temperature T∗=−1.2T∗=−1.2 K. This negative sign implies the presence of strong ferromagnetic correlations, as suggested from the previously reported magnetization data. The results indicate that the YbNiAl2 alloy is an antiferromagnetic Kondo lattice system with a similar energy scales of the Kondo and RKKY interactions.