  We consider the interplay between superconducting (SC) and commensurate
spin-density-wave (SDW) orders in iron-pnictides by analyzing a multiple order
Ginzburg-Landau free energy. We are particularly interested in whether the
doping-induced transition between the two states is first order, or the two
pure phases are separated by an intermediate phase with coexisting SC and SDW
orders. For perfect nesting, the two orders do not coexist, because SDW order,
which comes first, gaps the full Fermi surface leaving no space for SC to
develop. When nesting is not perfect due to either ellipticity of electron
bands or doping-induced difference in chemical potentials for holes and
electrons, SDW order still leaves modified Fermi surfaces for not too strong
SDW magnetism and the SC order may develop. We show that the two orders coexist
only when certain relations between ellipticity and doping are met. In
particular, in a compensated metal, ellipticity alone is not sufficient for
coexistence of the two orders.
