Evidence for nodal superconductivity in a layered compound Ta${}_4$Pd${}_3$Te${}_{16}$

We report an investigation of the London penetration depth $\mathrm{\Delta }\lambda (T)$ on single crystals of the layered superconductor Ta${}_4$Pd${}_3$Te${}_{16}$, where the crystal structure has quasi-one-dimensional characteristics. A linear temperature dependence of $\mathrm{\Delta }\lambda (T)$ is observed for $T\ll T_c$, in contrast to the exponential decay of fully gapped superconductors. This indicates the existence of line nodes in the superconducting energy gap. A detailed analysis shows that the normalized superfluid density ${\rho }_s(T)$, which is converted from $\mathrm{\Delta }\lambda (T)$, can be well described by a multigap scenario, with nodes in one of the superconducting gaps, providing clear evidence for nodal superconductivity in Ta${}_4$Pd${}_3$Te${}_{16}$.