The blast-wave at the edge of the supernova remnant IC443 is colliding with nearby quiescent gas. In this paper a multi-transition study of CO J = 1 - 0 → J = 4 - 3 is presented of one of these clouds, IC443C, and the detection of atomic carbon, CI, reported. The CO is optically thin with Tex ~ 45K, a measured isotopic ratio CO/13CO = 80, and N(CO) ~ 2 - 4 1017. Atomic carbon emission was detected for the first time in shocked gas only towards the IC443C C-shocked region, with an abundance ratio CI/CO ~ 1.3 - 2.9. CI is overabundant by one order of magnitude compared with quiescent molecular cloud cores, suggesting that shock(s), or an enhanced cosmic ray flux density, has increased the CI/CO ratio. A narrow CO absorption line towards the shocked region IC443G has Tex ~ 13-18K, and nH2 ~ 2-3 103 cm-3, which may be typical of conditions in the pre-shock gas
