Abstract
The anisotropic superconducting properties of a RbxFe2−ySe2 single crystal with Tc≃32 K were investigated by means of superconducting quantum interference device (SQUID) and torque magnetometry, probing the effective magnetic penetration depth λeff and the magnetic penetration depth anisotropy γλ. Interestingly, γλ is found to be temperature independent in the superconducting state but strongly field dependent: γλ(0.2 T)<4 and γλ(1.4 T)>8. This unusual anisotropic behavior, together with a large zero-temperature λeff(0)≃1.8 μm, is possibly related to a superconducting state heavily biased by the coexisting antiferromagnetic phase.