2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/22541We report microwave surface impedance measurements made on a single crystal of PrOs_4Sb_12 across the frequency range 0.5 to 21 GHz. The penetration depth data provide clear thermodynamic evidence for superconductivity arising in two bands coupled by Josephson pair-tunneling, indicating two order parameters with the same symmetry. Detailed conductivity spectra obtained using high-resolution bolometry confirm this picture and extend it, revealing the itinerant nature of the Pr f electrons through the observation of quasiparticles with heavily renormalized mass.5 pages, 4 figuresSuperconductivityStrongly Correlated Electronstext