One SIM card shared between two devices - IC?
It's not possible to share one SIM between two devices.

Well, not easily, anyway. The SIM contains a microcontroller and there is quite a complex communication protocol between it and the device it's installed in that would be confused by connecting two devices to the same SIM. That's in addition to the fact that the two devices would often be trying to drive the same SIM input pins to opposing states at the same time.

You would need to implement an intelligent device that would provide two SIM interfaces, one to each device, and a third interface to the SIM itself, and maintain a separate channel of communication for each interface.

Some service providers allow two SIMs to share the same plan, which is about as close as you're going to get without a great deal of work.