Simultaneous enhancements of Curie temperature and magnetocaloric effects in the La1−xCexFe11.5Si1.5Cy compounds

► Partial replacement of La with Ce leads to decrease in TC and an increase in ΔSM. ► Introduction of interstitial C atoms can adjust TC to high temperature. ► Carbonization results in reduction of both hysteresis loss and MCE. ► Two different approaches used to evaluate the effective refrigerant capacities. ► Enhancements of both TC and MCEs can be achieved simultaneously.