Reflectivity of a B-doped diamond film in the sub-THz region at different T normalized to its value at 10 K. The lines are fits obtained by assuming a BCS reflectivity below Tc and a Hagen-Rubens model at 10 K. The inset shows on the left scale the magnetic moment of the sample, as cooled either in a 10 Oe field (FC) or in zero field (ZFC), on the right scale its resistance normalized to its value at 12 K. The FC values are multiplied by 10.
