Hi
What I understand is, Seebeck effect is just the first Thomson effect (Thermal gradient on single conductor creating an electromotive force) for the both conductors in thermocouple.

But how is Peltier effect explained with Thomson effect?

Second Thomson effect states that current on a conductor with thermal gradient makes one part of the conductor heat up and another part cool down due to the current being resisted or accelerated by the electromotive force created by the thermal gradient.

Because Peltier effect means cooling and heating of junctions in thermocouple, maybe there's some kind of EMF at the junctions (electrochemical)?