To further clarify what Adam meant, it does indeed support all SDXC cards, you just have to have your K-5 running firmware version 1.02 or higher - To update, simply visit your localized Pentax site(For you -
Pentax Canada | PENTAX Firmware Update Software for K-5 ) and follow the instructions to update. You will need to charge your battery to full though, as a heads up.
Updating firmware also has benefits, such as better low light AF, and seemingly(Though not confirmed, only suspected by me and a few other members) faster screw-drive AF.(My 28-80 SMC sounds terrifying when it focuses now, as there are no rubber stoppers at the end of the focus path[Makes a loud *CLACK* when it reaches the edge])