  Critical fields of four MgB2 thin films with a normal state resistivity
ranging from 5 to 50 mWcm and Tc from 29.5 to 38.8 K were measured up to 28 T.
Hc2(T) curves present a linear behavior towards low temperatures. Very high
critical field values have been found, up to 24 T along the c-axis and 57 T in
the basal plane not depending on the normal state resistivity values. In this
paper, critical fields will be analyzed taking into account the multiband
nature of MgB2; we will show that resistivity and upper critical fields can be
ascribed to different scattering mechanisms.
