Stargate Search

I'm looking for a specific crossover. In it, Jack discovers Clark is an alien when clark is still a child (maybe a teenager). Later, when Clark is in trouble because Lionel Luthor (?) has found out he's an alien and Lex Luthor warns him, Clark's father sends him to Jack. Jack then arranges for Clark to go undercover as a master-seargant (I think) to Atlantis. In Atlantis, only Sheppard, McKay and Beckett know the truth. Eventually, someone from Clark's past (Lex' ex-wife) turns out to be there as well, as a spy for the trust, and Clark 'outs' himself to save all of Atlantis. I'm not sure, but I think Lex comes to visit him in Atlantis and Clark's Dad dies sometime during the story and Lex supports Martha because Clark can't be there.

I hope someone will be able to recognise this and tell me where it is, because I've searched by myself already and I haven't been able to find it.

I tagged the post with open, but I couldn't find a Smallville crossover tag, nor a general one.