  The interplay between superconductivity (SC) and spin/charge density wave
(DW) in organic metals shows many similarities to high-$T_c$ superconductors.
It also contains many puzzles, for example, the anisotropic SC onset observed
and the severalfold increase of the upper critical field $H_{c2}$ in the
coexistence region, as well as the microscopic origin of SC/DW phase separation
there. In this paper, by the direct calculation of the Landau expansion for DW
free energy, we argue that the phase transition between DW and metallic/SC
phase in organic superconductors goes by first order at low enough temperature,
which explains the spatial segregation of DW and SC at large length scale,
consistent with experimental observations. This first-order phase transition is
not directly related to SC and happens even above the SC transition
temperature.
