Spellstrike | Pathfinder Wrath of the Righteous Wiki

At 2nd level, whenever a magus casts a spell with a range of "touch" from the magus spell list, he can deliver the spell through any weapon he is wielding as part of a melee attack.
Instead of the free melee touch attack normally allowed to deliver the spell, a magus can make one free melee attack with his weapon (at his highest base attack bonus) as part of casting this spell. If successful, this melee attack deals its normal damage as well as the effects of the spell. If the magus makes this attack in concert with spell combat, this melee attack takes all the penalties accrued by spell combat melee attacks.
This attack uses the weapon's critical range (20, 19-20, or 18-20 and modified by the keen weapon property or similar effects), but the spell effect only deals x2 damage on a successful critical hit, while the weapon damage uses its own critical modifier.