Magnetic and electrical characterization of lanthanum superconductors   with dilute Lu and Pr impurities
  In this work we present measurements of the electrical conductivity and of the magnetization of La and of La-Pr and La-Lu dilute (up to 2 atomic percent) alloys, from which we determine, very in particular, the influence of dilute magnetic impurities on the upper critical magnetic field amplitude [and then on the superconducting coherence length amplitude and on the Ginzburg-Landau parameter]. 
F. Soto, L. Cabo, J. Mosqueira, F. Vidal