Based on the electronic structure of C 70 and ionic radii of alkali metal atoms, we propose an alkali-doped C 70 conductor Na 2CsC 70. The material is predicted to have a half-filled conduction band with a large Fermi-level density of states similar to alkali-doped C 70 superconductors. Since the conduction-band electronic states in Na 2CsC 70 reside mostly on 60 C sites having the same CC network curvature as that of C 60, its electron-phonon coupling should be strong. Hence, Na 2CsC 70 is a good candidate as a superconducting doped large fullerene.