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We measure magnetotransport of F doped SmFeAsO samples up to 28T and we extract the upper critical fields, using different criteria. In order to circumvent the problem of criteriondependence H c2 values, we suggest a thermodynamic estimation of the upper critical field slope dH c2 /dT based on the analysis of conductivity fluctuations in the critical regime. A high field slope as large as -12T/K is thus extracted for the optimally doped sample. We find evidence of a twodimensional lowest Landau level (LLL) scaling for applied fields larger than μ 0 H LLL ∼8T. Finally, we estimate the coherence length values and we observe that they progressively increase with decreasing T c . In all cases, the coherence length values along the c axis are smaller than the interplanar distance, confirming the two-dimensional nature of superconductivity in this compound.

We study the effect of neutron irradiation on the critical current density J c of isotopically pure polycrystalline Mg 11 B 2 samples. For fluences in the range 10 17 -10 18 cm -2 , J c is enhanced and its dependence on magnetic field is significantly improved: we demonstrate that, in this regime, pointlike pinning centers are effectively introduced in the system proportionally to the neutron fluence.Instead, for larger fluences, a strong suppression of the critical temperature accompanied by a decrease of both the upper critical field B c2 and J c is found.

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