Yes, the Samsung PRO Plus 256GB SD is compatible with the Sony A7 IV.
The samsung pro plus 256gb sd is a UHS-I U3/V30 card. On the A7 IV, U3/V30 clears standard XAVC S/HS 4K (200Mbps) and below, but not S&Q 4K (V60) or XAVC S-I 4K (V90). Records standard 4K, not the high-bitrate modes.
Limitation
Cannot record XAVC S-I 4K (Intra-frame) -- requires Video Speed Class V90, this card is V30. Works for XAVC HS 4K (Long GOP) and all lower-bitrate modes; card runs at UHS-I speed in the UHS-II slot.
“XAVC S-I 4K 600Mbps CFexpress Type A memory card (VPG200 or higher) SDXC V90 or higher”
“UHS-I Speed Class 3 (U3) and Class 10 for 4K UHD and FHD video”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)