Must I already be employed by the company abroad before an ICT transfer?

The whole concept of an Intra-Corporate Transfer is that an existing employee moves within the same business. To qualify, you must be employed in a unit of an undertaking that is headquartered in another EU state or outside the EU and then transferred to the German entity of that same group.

This means the ICT Card is not a route for joining a German company as a brand-new external hire. Your prior and continuing employment relationship with the sending unit abroad is what makes the transfer eligible, so be ready to document that relationship clearly.