Connect two 2-pole breakers together?

I have one of these thin dual circuit breakers Can I only two breakers in one slot A tandem breaker is a breaker that provides two separate and different circuits in the same circuit breaker slot Said breaker slot can be completely regular- two slot Both A and B circuits of a tandem breaker unit use the same phase, or incoming service leg corresponding to that slot 120V circuits use one leg

two breakers in one slot Both “hots” need protection from overcurrent, so we use a double-pole breaker that accepts two wires instead of one These breakers are larger