Unconventional superconductivity in the cage-type compound Sc 5 Rh 6 Sn 18

We have examined the superconducting ground-state properties of the caged-type compound Sc5Rh6Sn18 using magnetization, heat capacity, and muon-spin relaxation or rotation (μSR) measurements. Magnetization measurements indicate type-II superconductivity with an upper critical field of μ0Hc2(0)=7.24T. The zero-field-cooled and field-cooled susceptibility measurements unveil the onset of a diamagnetic signal below Tc=4.4K. The interpretation of the heat-capacity results below Tc using the α-BCS model unveils the value of α=2.65, which gives the dimensionless ratio 2Δ(0)/kBTc=5.3, intimating that Sc5Rh6Sn18 is a strong-coupling BCS superconductor. The zero-field μSR measurements in the longitudinal geometry exhibit a signature of the spontaneous appearance of the internal magnetic field below the superconducting transition temperature, indicating that the superconducting state is characterized by the broken time-reversal symmetry (TRS). We have compared the results of broken TRS in Sc5Rh6Sn18 with that observed in R5Rh6Sn18(R=Lu and Y).