Yes, the Lexar Professional CFexpress Type A Gold 256GB is compatible with the Sony Alpha A9 III.
Sony A9 III accepts CFexpress Type A in both combo slots. Lexar Gold Type A is VPG400 rated, meeting all A9 III recording formats including XAVC S-I 4K and S&Q Motion 4K (both require VPG200 minimum).
“XAVC HS 4K 280Mbps CFexpress Type A memory card (VPG200 or higher) XAVC S-I 4K 600Mbps CFexpress Type A memory card (VPG200 or higher)”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)