We consider electrons on a honeycomb or triangular lattice doped to the saddle point of the bandstructure. We assume system parameters are such that spin density wave (SDW) order emerges below a temperature T_N and investigate the nature of the SDW phase. We argue that at T < T_N the system develops a uniaxial SDW phase whose ordering pattern breaks O(3) × Z_4 symmetry and corresponds to an eight site unit cell with non-uniform spin moments on different sites. This state is a half-metal -- it

more »

... eserves full original Fermi surface, but has gapless charged excitations in one spin branch only. It allows for electrical control of spin currents and is desirable for nano-science.