ak47jar3d :
I would say get no less Class 10 SDHC UHS-I sd card.
SanDisk Ultra 64GB microSDXC UHS-I Card with Adapter, Grey/Red, Standard Packaging (SDSQUNC-064G-GN6MA) https://www.amazon.com/dp/B010Q588D4/ref=cm_sw_r_other_awd_mpSNwb9ZBM0TA
Thanks! I feared I would have to cash out on a class 10 card, but I guess it's better to be safe than sorry right?
I did manage to spot a Kingston 64GB MicroSD Class 10 UHS-I 45MB/s Read Card + SD Adapter that was quite cheaper than the card you suggested, so I guess I might go with that one. Apparently the write speed of the card is 10 MB/s which should be sufficient to handle the Xperia Z5's 7,5 MB/s bitrate right?
Gotta say on a general note that the memory card speed requirements for some cameras are a bit baffling to say the least. I purchased the Sony RX100M4 compact camera last year due to its 4K capabilites. The camera shoots 4K at a 100Mbps = 12,5 MB/s. Now I had a couple of Sandisk Extreme Pro SDHC Class 10 UHS-1 cards already from my previous camera. Now those cards are rated as having 95MB/s read and 90MB/s write speeds so they should be more than capable of handling recording video in a 12,5 MB/s bitrate right? No such luck. The option to record 4K was all greyed out and unavailable to me because the cards weren't rated as SDXC, only SDHC. And so I had to go out and buy brand new expensive SDXC rated cards just to record 4K with that camera. Weird.
Anyway, thanks.