Upper critical fields and two-band superconductivity in   Sr1-xEux(Fe0.89Co0.11)2As2 (x=0.203 and 0.463)
  The upper critical fields, Hc2 of single crystals of Sr1-xEux(Fe0.89Co0.11)2As2(x=0.203 and 0.463) were determined by radio frequency penetration depth measurements in pulsed magnetic fields. Hc2 approaches the Pauli limiting field but shows an upward curvature with an enhancement from the orbital limited field as inferred from Werthamer-Helfand-Hohenberg theory. We discuss the temperature dependence of the upper critical fields and the decreasing anisotropy using a two-band BCS model. 
Rongwei Hu, Eun Deok Mun, M. M. Altarawneh, C. H. Mielke, V. S. Zapf,   S. L. Bud'ko, P. C. Canfield
cond-mat.supr-con