Competing phases in the high field phase diagram of (TMTSF)$_2$ClO$_4$
  A model is presented for the high field phase diagram of (TMTSF)$_2$ClO$_4$, taking into account the anion ordering, which splits the Fermi surface in two bands. For strong enough field, the largest metal-SDW critical temperature corresponds to the N=0 phase, which originates from two intraband nesting processes. At lower temperature, the competition between these processes puts at disadvantage the N=0 phase vs. the N=1 phase, which is due to interband nesting. A first order transition takes then place from the N=0 to N=1 phase. We ascribe to this effect the experimentally observed phase diagrams. 
S. Haddad (1), S. Charfi-Kaddour (1), C. Nickel (2), M. H\'eritier (2)   and R. Bennaceur (1) ((1) LPMC, Facult\'e des Scien...