Microwave Properties of Ba(0.6)K(0.4)BiO(3) Crystals
  We report on field-induced variations of the microwave surface resistance at 9.6 GHz of Ba(0.6)K(0.4)BiO(3) crystals. Energy losses have been investigated as a function of the static magnetic field in the range of temperatures 4.2 K - Tc. By analyzing the experimental results in the framework of the Coffey and Clem model we determine the temperature dependence of the first-penetration field, upper critical field and depinning frequency. The results show that the pinning energy of this bismuthate superconductor is weaker than those of cuprates. 
S. Fricano, M. Bonura, A. Agliolo Gallitto, M. Li Vigni, L. A.   Klinkova, and N. V. Barkovskii