A novel non–Fermi-liquid state in the iron-pnictide FeCrAs

Abstract

We report transport and thermodynamic properties of stoichiometric single crystals of the hexagonal iron-pnictide FeCrAs. The in-plane resistivity shows an unusual "non-metallic" dependence on temperature T, rising continuously with decreasing T from ~800 K to below 100 mK. The c-axis resistivity is similar, except for a sharp drop upon entry into an antiferromagnetic state at TN~125 K. Below 10 K the resistivity follows a non–Fermi-liquid power law, ρ(T)=ρ0-ATx with x<1, while the specific heat shows Fermi-liquid behaviour with a large Sommerfeld coefficient, γ~30 mJ/mol K2. The high-temperature properties are reminiscent of those of the parent compounds of the new layered iron-pnictide superconductors, however the T→0 K properties suggest a new class of non-Fermi liquid.