An intriguing point is that in the resistivity, showing a metallic $T$-dependence down to low $T$ as well, no anomaly at around  is found [@Tanaka_2007CL]. Furthermore, the analysis of an NMR measurement [@Hara_2008JPSJ] suggests the magnetic moment in this AF state to be rather large, i.e., on the order of 1 $\mu_{\rm B}$. These features are distinct from the formation of a spin-density-wave state due to the nesting of Fermi surface, as frequently observed in CTS, where anomalies in transport properties appear and typical values of the magnetic moment are one order of magnitude smaller, or even less [@Review_2006JPSJ]. Such a magnetic solution attributed to the $p\pi$ bands is actually stabilized in first-principles calculations [@Ishibashi_2005JPSJ; @Ishibashi_2008JPSJ] as well as in a mean-field (MF) study of an effective Hubbard model [@Seo_2008JPSJ], which faces difficulties in explaining these experimental facts.

Recently, another isostructural member \[Cu(tmdt)$_2$\], having an odd number of electrons per unit cell, has been successfully synthesized [@Zhou_2010IC]. It shows a semiconductive behavior in contrast to the two compounds above, and exhibits an AF phase transition at  $=13$ K, much lower than in \[Au(tmdt)$_2$\] [@Zhou_2010IC; @Takagi_2012PRB]. The $T$ dependence of magnetic susceptibility above  is ascribed to the behavior of the one-dimensional 