  Linear diamagnetism is predicted in the vortex-liquid phase of layered
superconductors at temperatures just below the mean-field phase transition on
the basis of a high-temperature analysis of the corresponding frustrated XY
model. The diamagnetic susceptibility, and the Nernst signal by implication, is
found to vanish with temperature as (T_c0 - T)^3 in the vicinity of the
meanfield transition at T_c0. Quantitative agreement with recent experimental
observations of a diamagnetic signal in the vortex-liquid phase of
high-temperature superconductors is obtained.
