Comment on "Superconducting anisotropy and evidence for intrinsic pinning in single crystalline MgB2" -: art. no. 226501

In a recent paper [Phys. Rev. B 66, 012501 (2002)], torque data measured on a MgB2 single crystal in fields from 10 to 60 kOe at 10 K were presented. The authors obtained the anisotropy gamma by fitting a theoretical expression to the data and concluded that the anisotropy is field-independent, gammaapproximate to4.3. In this Comment, we show that the above conclusion does not hold, because it was obtained based on the analysis of torque data measured in fields close to or above the upper critical field H-c2, where the theoretical expression used is not applicable. Furthermore, we argue that the experimental torque data with Hmuch less thanH(c2) indicate an anisotropy strongly increasing with increasing field.