The superconducting upper critical field H-c2(T) of a two dimensional
BCS superconductor is calculated in the vicinity of a van-Hove singula
rity. The zero temperature upper critical field is strongly enhanced a
t weak coupling when the Fermi contour coincides with van-Hove points,
scaling as H-c2(0) proportional to T-c(root 2) compared to the usual
result H-c2(0) proportional to T-c(2). The result can be interpreted i
n terms of the unusual Fermi liquid decay of normal state pair correla
tions in the vicinity of a van-Hove point. Copyright (C) 1996 Elsevier
Science Ltd