How to set 5 GHz ad hoc network using a dual band 7260 802.11ac module

I am trying to set up an ad hoc network under both Windows 7 and Linux with these WiFi cards. However, whilst I can set up an ad hoc network at 2.4 GHz, I have not been able to do so at 5 GHz. There should be no regulatory reasons why I cannot do that in the UK.

Has anyone else been able to set up such an ad hoc network, and if so how?

I am using some Dell rugged laptops with the 7260s running either Windows 7, Ubuntu and Fedora.