${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$ is a diamagnetic metallic compound (space group: $I{4}_1/acd, a\approx 13.5\AA$, $c\approx 27.1\AA$) which becomes superconducting (sc) at $T_{\mathrm{c}}=5.15\mathrm{K}$. The sc state was studied on single-crystal samples by temperature- and field-dependent electrical resistivity, specific heat, and muon-spin rotation ($\mu \mathrm{SR}$) spectroscopy. No anisotropy of the upper critical field $B_{\mathrm{c}2}=7.75\mathrm{T}$ is observed. Analyses of specific heat indicate enhanced values of the jump $[\mathrm{\Delta }{c}_p/\left({\gamma }_{\mathrm{tot}}{T}_{\mathrm{c}}\right)=1.58]$ and of the energy gap ratio $[\mathrm{\Delta }\left(0\right)/\left(k_{\mathrm{B}}{T}_{\mathrm{c}}\right)=2.39]$ as well as an exponential decrease of the electronic contribution below $T_{\mathrm{c}}/2$. Together with the saturation of the superfluid density for $T<3\mathrm{K}$ observed by $\mu \mathrm{SR}$ spectroscopy these findings lead us to classify ${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$ as a moderately strong coupled isotropic $s$-wave superconductor. However, above $T_{\mathrm{c}}$, the crystals reveal a surprisingly anisotropic and large resistivity of $2.5–4.5\mathrm{m}\mathrm{\Omega }$ m with metalliclike behavior perpendicular to the $c$ axis and by a factor of $\sim 2$ larger parallel to $c$, which decreases upon increasing temperature. These observations are discussed in connection to a characteristic intrinsic disorder in the crystal structure of ${\mathrm{Sc}}_5{\mathrm{Rh}}_6{\mathrm{Sn}}_{18}$.

• Received 31 January 2020
• Revised 29 May 2020
• Accepted 23 June 2020

DOI:https://doi.org/10.1103/PhysRevB.102.024508