  By first principles method, we have determined the geometric configuration of
K/Ba-codoped phenanthrene based on the formation energy calculations, and
systematically investigated its electronic and magnetic properties. There are
two bands crossing Fermi energy which mainly result from the LUMO+1 orbitals of
two phenanthrene molecules in a unit cell, and the cylinder-like Fermi surface
along the ${\Gamma}$-Z direction reflects the two-dimension character of
metallic conduction of K/Ba-codoped phenanthrene. Compared to K-doped
phenanthrene, K/Ba-codoping can donate more electrons to molecule to modify the
electronic structure, while the intercalation of dopants does not result in the
large distortion of molecule. (KBa)$_1$phenanthrene is a magnetic metal with
the spin moment of 0.32 ${\mu}_B$ per each molecule, and unexpectedly, the
spins gather in one edge of molecule rather than a uniform distribution on the
whole molecule. Our results demonstrate that codoping of monovalent and
bivalent metals is an effective approach to modulate the electronic properties
of metal-doped hydrocarbons.
