Hello all,

All Psychic Powers have an XP value to learn, e.g. Mindprobe costs 200xp.

However there is also a Tier 1 Talent called Psychic Power (page 130) which says "...the character has learned an additional Psychic Power. This power may be selected from one of the powers presented in Chapter VI..."

So when purchasing a new power (such as a human Psyker spending his 1,000 xp at generation) do you have to buy the Talent (for 250 xp) and then pay for the Power (in this case 200 xp) making it cost 450 xp in total?

I think the answer is stated right after the sentence you quoted. The Talent says further “The experience cost and requirements for psychic powers are not the same as other Talents (as detailed on page 77) and can instead be found in Chapter VI: Psychic Powers.”
So I think it is pretty clear that you only pay the xp value indicated by the power.

Well yes it does say that but then I couldn't understand why it was listed as a Talent at all or quantified as Tier 1 (thus assigning it a cost).

So basically the Psychic Power talent sits outside the Tier system and when you buy a new power it costs anything from 100 xp to 1,000 xp as listed without any additional cost. That's what I thought when I first read it and when I tried character generation, then afterwards I saw the Talent and got confused.

Sort of. It still counts as a talent for the purpose of alignment with the chaos gods and what not (so a Nurgle power is for Nurgle alignment, etc. Anything non chaos god aligned is obviously unaligned).

It's also important for Minions who don't have XP, but talent "slots".