L level. The existence of two L sites in the unit cell, which show dimerization as discussed in the previous subsection, results in band splitting, but not large enough to generate a direct band gap. Then electron and hole pockets appear and compose the Fermi surface. This is how the first SCMC with a metallic character was realized.

Comparing the room-$T$ and low-$T$ structure parameters for \[Au(tmdt)$_2$\], the low-$T$ data show slightly larger transfer integrals than the room-$T$ data especially in L-L pairs; this is naturally expected from the thermal contraction. $\Delta_{\textrm{M}\sigma}^0$ is reduced by lowering $T$ by about 0.05 eV, which is consistent with the previous MO calculation [@Zhou_2009IC]. As a result, a fraction of electrons in the L sites, nearly 3/4-filled in the room-$T$ parameters, are transfered to the M$\sigma$ orbital in the low-$T$ parameters: {$\bar{n}_{\textrm{M}\sigma}$, $\bar{n}_{\textrm{L}}$} = {0.03, 1.5} (room-$T$) $\rightarrow$ {0.09, 1.47} (low-$T$).

As for \[Cu(tmdt)$_2$\], M$\sigma$ mixes more with L due to the further reduction in $\Delta_{\textrm{M}\sigma}^0$, by about 0.30 eV smaller than the low-$T$ parameter for \[Au(tmdt)$_2$\]. In particular, near $\epsilon_{\rm F}$, the contribution of M$\sigma$ is appreciable [@Ishibashi_2012Crystals], even though the orbital level scheme shows a positive $\Delta_{\textrm{M}\sigma}^0$. This is because L orbitals 