also realized in some CTS as notably discussed in $M$(dmit)$_2$-based compounds. [@Canadell_1989JP; @RKato_2004CR] The first SCMC in which metallic conductivity was reported [@Tanaka_2001Science] is \[Ni(tmdt)$_2$\] (tmdt = trimethylene-tetrathiafulvalene-dithiolate), [@noteSqBr] whose resistivity decreases by cooling down to lowest temperatures ($T$). Direct evidence of its metallic feature was given by the observation of three-dimensional Fermi surfaces by de Haas-van Alphen oscillations [@Tanaka_2004JACS], whose results are consistent with first-principles band calculations [@Tanaka_2004JACS; @Rovira_2002PRB]. Near the Fermi energy $\epsilon_{\rm F}$, there exist two overlapping bands from different $p\pi$-type MO and $\epsilon_{\rm F}$ crosses the overlapping area. Electron and hole pockets appear, owing to the existence of an even number of electrons in the unit cell consisting of one Ni(tmdt)$_2$ molecule. This is the success of the molecular design mentioned above. It shows Pauli paramagnetic susceptibility, [@Tanaka_2001Science] while isotropic magnetoresistance suggesting the spin effect is observed [@Yasuzuka_2008JPSJ] whose origin remains unclear.

Since the discovery of \[Ni(tmdt)$_2$\], many related compounds have been synthesized. Among them, an isostructural analog but with an odd number of electrons per unit cell, \[Au(tmdt)$_2$\] [@Suzuki_2003JACS], has been attracting interest. It shows an antiferromagnetic (AF) phase transition with a transition temperature  $=110$ K [@Zhou_2006JACS; @Hara_2008JPSJ], which is exceptionally high among molecular conductors. 