hi can i increment for 4MT08C5100 in sql?

create an ID INT IDENTITY column and use that as your primary key (it's unique, narrow, static - perfect)
if you really need an ID with a letter or something, create a computed column based on that ID INT IDENTITY

Try something like this:

CREATE TABLE Demo(ID INT IDENTITY PRIMARY KEY,
                      IDwithChar AS '4MT08' + RIGHT('5100' + CAST(ID AS VARCHAR(10)), 6) PERSISTED)

This table would contain ID values from 1, 2, 3, 4........ and the IDwithChar would be something like 4MT085100, 4MT085101, ....., 4MT085199 and so forth.

With this, you have the best of both worlds:

-A proper, perfectly suited primary key (and clustering key) on your table, ideally suited to be referenced from other tables.

-Your character-based ID, properly defined, computed, always up to date