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

We report an investigation of the London penetration depth $Deltalambda(T)$ 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 $Deltalambda(T)$ is observed for $Tll T_c$, 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 $Deltalambda(T)$, 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$_{16}$.