Is this binding compatible with a Garmont AT boot sole?

Kinda, but it's not advised (by manufacturers or shops) to ski an AT sole in an alpine binding. Usually, there are two problems: an AT sole is thicker than an Alpine DIN sole and put upward pressure on the toe piece that could cause the binding to break, but with the adjustable toe-piece (AFD) height in this binding, you should be able to negate that with some adjustments. Of bigger concern is the lateral release, since AT soles are vibram (or similar) rubber they will not slide off of the AFD when the toe piece tries to release laterally. AT bindings have AFDs that either slide laterally or are made of a different material. Loads of people take the risk and ride AT boots (a fair few patrollers where I work) and I've heard many of them say that they have turned down their toe DIN (-2 usually), but they still risk a twisted knee or worse. All that to say, it can be done, but not without risk to your gear and body.

Negative, you need alpine soles on your boots for these bindings.