brb pp.50
These powers vary from race to race and sometimes from one individual psyker to another. The psychic powers availale to our models are not discussed further here, but are described in detail in the Codexes, where you will find complete rules for individual powers.
codex GK pp.51
Only one Psychic Barrage is 'fired', regardless of the number of psykers in the squad. All psykers in the same unit are treated as a single psyker for the purposes of Pshchic tests, ets, and use their own Leadership value, not that of any attached characters.
Psychers have psychic power, a squad of psykers counts as a single psyker... please explain how you have a leg to stand on. This is about as clear cut as you can get.