Yes, the Samsung PRO Plus 256GB SD is compatible with the Sony Alpha 1.
Samsung Pro Plus is UHS-I (not UHS-II). Sony A1 supports UHS-I for still images and XAVC S HD at 100Mbps (requires U3 or higher — Pro Plus is U3). Higher video formats (4K and above) require UHS-II or CFexpress Type A.
Conditions for compatibility
Compatible for still image shooting and XAVC S HD video at 100Mbps (U3 requirement met). Incompatible with all 4K recording formats — those require SDXC UHS-II (V60 minimum) or CFexpress Type A. Not a viable card for A1 video work.
“XAVC S HD 100Mbps CFexpress Type A memory card SDHC/SDXC card (U3 or higher)”
Last verified:
Confidence: inferred