Low-temperature thermal conductivity measurements were performed on the single crystal of caged-type superconductors Y 5 Rh 6 Sn 18 and Lu 5 Rh 6 Sn 18 down to 80 mK. In zero magnetic field, no residual linear term T 0 k is found for either superconductor. At low field, the T 0 k of these two superconductors shows weak field dependence. These results exclude the nodal superconducting gap in Y 5 Rh 6 Sn 18 as revealed by recent specific heat measurements, and suggest that the caged-type superconductors R 5 Rh 6 Sn 18 (R = Y and Lu) may have a common nodeless superconducting gap.

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