The Alpha 7 wasn't supported until Camera Raw 8.3 at the end of last year. ACR 8.3 only works in CS6/CC.
I recommend using the latest available version of Camera Raw for each version of CS, which in your case (CS5) is 6.7.1. The latest versions are usually the best, fixing the most bugs and containing refinements missing from earlier versions.
The cheapest way to carry on with CS5 is to download Adobe DNG Converter, and batch-convert folders of your Alpha files to DNG. It's an extra step after downloading your images, but it's free.
Camera Raw 6.7.1 and DNG Converter 8.6 are both available from the downloads section of the Adobe website. Please note that you may need DNG Converter 8.3 if you are still running CS5 on XP/Vista or (Snow-) Leopard.
Photoshop Lightroom is designed by the same team which writes Camera Raw and uses very similar programming. Consequently, it works in a similar way to Camera Raw (with Bridge) and is updated at the same time—following its version numbering by a increment of 3 (currently Lightroom 5.6). You could buy Lightroom and use it to import and convert your raw files without using DNG Converter and Camera Raw. It's a Marmite thing: some people love it, some don't. You can probably download a free trial and find out for yourself. Once you have converted your images in Lightroom, you can export them to Photoshop CS5 for editing.
Thanks so much for the help!