We report muon spin rotation (${ \mu}$SR) experiments on the microscopic properties of superconductivity and magnetism in the kagome superconductor CeRu$_{ 2}$ with $T_{ \rm c}$~${ \simeq}$~5~K. From the measurements of the temperature-dependent magnetic penetration depth ${ \lambda}$, the superconducting order parameter exhibits nodeless pairing, which fits best to an anisotropic $s$-wave gap symmetry. We further show that the $T_{ \rm c}$/$\lambda^{ -2}$ ratio is comparable to that of unconventional superconductors. Furthermore, the powerful combination of zero-field (ZF)-${ \mu}$SR and high-field ${ \mu}$SR has been used to uncover magnetic responses across three characteristic temperatures, identified as $T_1^*$~${ \simeq}$~110~K, $T_2^*$~${ \simeq}$~65~K, and $T_3^*$~${ \simeq}$~40~K. Our experiments classify CeRu$_{ 2}$ as an exceedingly rare nodeless magnetic kagome superconductor.
Categories: cond-mat.supr-con cond-mat.mtrl-sci