Abstract
-YbAlB is the locally isostructural polymorph of -YbAlB, the first example of a Yb-based heavy fermion superconductor that exhibits pronounced non-Fermi-liquid behavior above . Interestingly, both -YbAlB and -YbAlB have strongly intermediate valence. Our single-crystal study of the specific heat, magnetization, and resistivity has confirmed the Fermi-liquid ground state of -YbAlB in contrast to the quantum criticality observed in -YbAlB. Both systems exhibit Kondo lattice behavior with the characteristic temperature scale K in addition to a valence-fluctuation scale K. Below , -YbAlB forms a heavy-Fermi-liquid state with an electronic specific heat coefficient mJ/mol K and a large Wilson ratio greater than 7, which indicates ferromagnetic correlation between Yb moments. A large anisotropy in the resistivity, which is one of the largest in heavy fermions, suggests that the hybridization between 4 and conduction electrons is much stronger in the plane than along the axis, indicating this is an excellent system to study for revealing the anisotropic hybridization effects. The strongly anisotropic hybridization as well as the large Wilson ratio is the key to understanding the unusual Kondo lattice behavior and heavy-fermion formation in mixed-valence compounds.
- Received 11 May 2011
DOI:https://doi.org/10.1103/PhysRevB.84.125126
©2011 American Physical Society