Weak Phan systems of type Cn

The present article provides a classification of noncollapsing Phan amalgams of type Cn and of shape S S2 over finite fields of square order distinct from four. Together with the results of [R. Gramlich, C. Hoffman, S. Shpectorov, J. Algebra 264 (2003) 358–384] this completes the proof of a Phan-type theorem for the group Sp2n(q) for sufficiently large n and q.