Upper critical magnetic field of the superconducting heavy fermion system (U1−x Thx)Be13

Abstract
Measurements of the ac electrical resistance as a function of temperature and applied magnetic field R(T,H) were made for various compositions x≲0.03 in the mixed binary system (U1−xThx)Be13. All samples within this range of x exhibit heavy Fermion superconductivity with a superconducting transition temperature Tc that is rapidly suppressed by the substitution of Th for U. The shape of the upper critical field curve Hc2(T) determined from the R(T,H) data is similar for all compositions with a very large initial slope (−dHc2/dT)Tc.