Outflank

Outflank (Teamwork)
You look for every edge when flanking an enemy.
Prerequisite: Base attack bonus +4.
Benefit: Whenever you and an ally are flanking the same creature, your flanking bonus on attack rolls increases to +4. In addition, whenever you score a critical hit against the flanked creature, it provokes an attack of opportunity from your ally.

OPEN GAME LICENSE Version 1.0a - All text is Open Game Content.