  In a two-band superconductor, two qualitatively different fluctuation modes
related to the gap modules contribute to free energy and heat capacity, in
addition to the phase fluctuations. The first mode has divergent temperature
behaviour since it accounts for the critical fluctuations around the phase
transition point, Tc, along with pseudo-critical ones associated with former
instability of the weaker-superconductivity component. The involvement of these
two factors, competing under interband interaction, results in the Ginzburg
number which increases with Tc non-monotonically, allowing the reduction up to
75%. This makes fluctuations effective for revealing additional superconducting
component in the system. The second mode does not diverge, but has a jump at
Tc, defined uniquely by the strength of interband interaction. This mode
contributes fundamentally beyond critical domain.
