  We investigate the influence of order parameter fluctuations on the
transition between normal and mixed superconducting states at low temperatures.
We show that in case of clean quasi-two-dimensional superconductors the
transition can be described by the functional of the Ginzburg-Landau type. We
consider the large-N generalization of this functional and using the lowest
Landau level approximation we get the large-N equations which describe the
phase transition. In case of physical dimensionality we found that the
transition is of the first order. The fluctuations significantly affect the
temperature dependence of the upper critical field.
