International audienceThe low-lying structure of 15C has been investigated via the neutron-removal 16C(d,t) reaction. Along with bound neutron sd-shell hole states, unbound p-shell hole states have been firmly confirmed. The excitation energies and the deduced spectroscopic factors of the cross-shell states are an important measure of the [(p)−1(sd)2] neutron configurations in 15C. Our results show a very good agreement with shell-model calculations using the SFO-tls interaction for 15C. However, a modification of the p-sd and sd-sd monopole terms was applied in order to reproduce the N=9 isotone 17O. In addition, the excitation energies and spectroscopic factors have been compared to the first calculations of 15C with the abinitio self-consistent Green's function method employing the NNLOsat interaction. The results show the sensitivity to the size of the N=8 shell gap and highlight the need of going beyond the current truncation scheme in the theory