  Using various transport and magnetotransport probes we study the coexistence
of spin-density wave and superconductor states in (TMTSF)2ClO4 at various
degrees of ClO4 anions ordering. In the two-phase complex state when both
superconductivity and spin-density wave are observed in transport, we find
prehistory effects, enhancement of the superconducting critical field, and
strong spatial anisotropy of the superconducting state. These features are
inconsistent with the conventional model of structural inhomogeneities produced
by anion ordering transition. We reveal instead that superconductor and
spin-density wave regions overlap on the temperature -- dimerization gap V
phase diagram, where V is varied by anion ordering. The effect of anion
ordering on (TMTSF)2ClO4 properties is thus analogous to that of pressure on
(TMTSF)2X (X=PF6 or AsF6), thereby unifying general picture of the coexistence
of superconductivity and spin-density wave in these compounds.
