  We report the single-crystal synthesis and detailed investigations of the
cage-type superconductor Sc5Ru6Sn18, using powder x-ray diffraction (XRD),
magnetization, specific-heat and muon-spin relaxation (muSR) measurements.
Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with
the lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC
magnetization measurements prove the type-II superconductivity in Sc5Ru6Sn18
with Tc = 3.5(1) K, a lower critical field H_c1 (0) = 157(9) Oe and an upper
critical field, H_c2 (0) = 26(1) kOe. The zero-field electronic specific-heat
data are well fitted using a single-gap BCS model, with superconducting gap =
0.64(1) meV. The Sommerfeld constant varies linearly with the applied magnetic
field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and
transverse-field (TF) muSR measurements reveal that Sc5Ru6Sn18 is a
superconductor with strong electron-phonon coupling, with TF-muSR also
suggesting the single-gap s-wave character of the superconductivity.
Furthermore, zero-field muSR measurements do not detect spontaneous magnetic
fields below Tc, hence implying that time-reversal symmetry is preserved in
Sc5Ru6Sn18.
