What is the maximum MTU of the C5C? .I want to use MPLS

Is it possible to increase the mtu of mimosa C5C ?.

If not possible, what is the maximum MTU to work MPLS?

The MTU of the PTP antennas are not adjustable. Though they can adjust. As long as you have MCS of above 7 you should be good up to 3200 MTU.