We report the observation of a new band system of C-2, namely, the 4(3)Pi(g)-a(3)Pi(u), system. The bands, observed by resonant 2-photon ionization spectroscopy and time-of-flight mass spectrometry, were identified through a synergy of high-level ab initio computation and double-resonance spectroscopy. Two bands are firmly identified, 1-3 and 0-2, allowing the 4(3)Pi(g) origin to be placed at 51496.44 cm(-1). The 4(3)Pi(g) state is, characterized as having a single bond, with a vibrational frequency of about 1268 cm(-1), and an equilibrium bond length of 1.57 angstrom. The state is predicted to exhibit a barrier to dissociation, with a rotational constant that unusually increases with vibrational excitation up to a maximum before decreasing at higher vibrational excitation. The new band system allows us to probe the a(3)Pi(u) state of C-2 through a straightforward 1 + 1 REMPI scheme.