You have an '06 XK? I didn't think the FOBIK key were available to later years.
This is a FOBIK key.
If you have a transponder key with a remote built into the key head, it looks like this.
No, transponder and FOBIK keys work on different technology. The transponder key wouldn't physically fit the key hole of the ignition anyway, let alone the module NOT being able to talk to the key or the transponder be programed for it in anyway.
If you have a true FOBIK, what you need is a POD key.
The POD key has the RFID chip in it, like the FOBIK key, and it can be programmed for you vehicle and it will fit the ignition.
A spare key like a hide-a-key. Personally I don't like the idea of the FOBIK/XPDR key hanging off a magnet under the vehicle to get lost. The system is setup to only make so many key copies, like 7 or 8, and it won't make anymore. I get a cheap key made that is only capable of opening the door lock, put that in the hide-a-key under the car. Then I have a spare POD/simple XPR key in the back with the jack. So I loose the key, I use the hide-a-key to open the door and then get the more valuable POD/XPDR key hidden in the back that won't get lost.