$c$-axis transport in UTe${}_2$: Evidence of Three Dimensional Conductivity Component

Abstract

We study the temperature dependence of electrical resistivity for currents directed along all crystallographic axes of the spin-triplet superconductor UTe${}_2$. We focus particularly on an accurate determination of the resistivity along the $c$-axis ($\ddot{I}{}_c$) by using a generalized Montgomery technique that allows extraction of crystallographic resistivity components from a single sample. In contrast to expectations from the observed highly anisotropic band structure, our measurement of the absolute values of resistivities in all current directions reveals a surprisingly nearly isotropic transport behavior at temperatures above Kondo coherence, with $\ddot{I}{}_c\sim \ddot{I}{}_b\sim 2\ddot{I}{}_a$, that evolves to reveal qualitatively distinct behaviors on cooling. The temperature dependence of $\ddot{I}{}_c$ exhibits a peak at a temperature much lower than the onset of Kondo coherence observed in $\ddot{I}{}_a$ and $\ddot{I}{}_b$, consistent with features in magnetotransport and magnetization that point to a magnetic origin. A comparison to the temperature-dependent evolution of the scattering rate observed in angle-resolved photoemission spectroscopy experiments provides important insights into the underlying electronic structure necessary for building a microscopic model of superconductivity in UTe${}_2$.