Deviation from the Kadowaki–Woods relation in Yb-based intermediate-valence systems

The T²-coefficient of the electrical resistivity, A, is compared with the electronic specific heat coefficient, γ, for a number of Yb-based compounds. It is revealed that many systems, including YbCuAl, YbInCu₄, YbAl₃, and YbCu₅, show A/γ² values close to 0.4 × 10⁻⁶ μΩ cm mol² K² mJ⁻², which are remarkably small compared to those obtained from an expression known as the Kadowaki–Woods relation: A/γ² = 1.0 × 10⁻⁵ μΩcm mol² K² mJ⁻². Empirically, the compounds with the smaller A/γ² values appear to show weak intersite magnetic correlation and/or to have almost fully degenerate (J = 5/2 or 7/2) ground states.