  The ongoing search for new superconductors has recently yielded a new family
of oxypnictides composed of alternating La_2O_{2-x}F_x and Fe_2As_2 layers
[1-4] with transition temperatures T_c of 25-28 K, which can be raised to 40-43
K by replacing La with Ce [5] or Sm [6] or to 52 K by replacing La with Nd and
Pr [7, 8]. Recent experiments and band structure calculations have suggested an
unconventional multiband superconductivity in the layers of paramagnetic Fe
ions, which would normally destroy superconductivity in the traditional
mechanism of the s-wave Cooper pairing. Here we report very high-field
resistance measurements up to 45T, which show a remarkable enhancement of the
upper critical fields B_c2 at low temperatures, as compared to those expected
from the already high slopes of dB_c2/dT ~ 2T/K near T_c . The deduced B_c2(0)
~ 63-65 T exceeds the paramagnetic limit, consistent with strong coupling and
important two-band effects in LaFeAsO_0.89F_0.11. We argue that oxypnictides
are emerging as a new class of high-field superconductors surpassing the B_c2
of Nb_3Sn, MgB_2, and the Chevrel phases and perhaps approaching the 100T field
benchmark of the high-T_c cuprates.
