MEASUREMENTS OF THE UPPER CRITICAL-FIELD OF K3C60 AND RB3C60 POWDERS TO 60-T

The onset of the upper critiCal field B(c2)(7) measured up to 60 T in powdered single-phase K3C60 and Rb3C60 yields T(c) = 19.5 and 28.4 K, B(c2)(4.2 K) = 30 and 55 T, (d(Bc2)/dT)T=T(c) = -2, 80 and -3.85 T/K, and Ginzburg-Landau coherence lengths at 0 K of 31 and 24 angstrom, respectively. B(c2)(T) appears to be that of a "conventional" superconductor showing paramagnetic limiting. These measurements are with earlier data and qualitative and quantitative differences are discussed.