a molecule become antiparallel [@Ishibashi_2005JPSJ]. The results of the first-principles calculation [@Ishibashi_2005JPSJ] correspond to the case of relatively small $U_\textrm{L}$ , and the system remains metallic even in the L-AF state.

On the other hand, in the case of \[Cu(tmdt)$_2$\], a stable AF pattern shows spin moments on both L and M$\sigma$ sites when both $U_{\textrm{M}}$ and $U_{\textrm{L}}$ are large enough; it is then denoted as L&M$\sigma$-AF. As shown in Fig. \[fig5\](c), spins on L sites show a staggered AF state, in which those connected with A, B, and Q (see Fig. \[fig3\]) bonds are antiparallel; the $t_{lm}$ values are large along these L-L bonds, as shown in Table \[table1\]. Spins on M$\sigma$ sites are also staggered, with the common spin ordering vector $q_\textrm{mag}[\textrm{L}]=q_\textrm{mag}[\textrm{M}\sigma]=(\pi,\pi,0)$. This can open an insulating gap when both L and M$\sigma$ bands becomes nearly 1/2-filled; both orbitals provide effective $S=$ 1/2, and the AF pattern corresponds to the N[' e]{}el state configuration. Now, this can be considered as a multiband Mott insulator, due to the quasi-degeneracy of the two orbitals.

The two contrasting situations for large interactions are summarized in Fig. \[fig5\](d), where schematic representations of electron occupancies in the two cases are shown. In the 