Yes, the Sony Alpha A9 III is compatible with the Transcend 700S V90 64GB.
Transcend 700S V90 is V90 class. Clears: XAVC S HD (100 Mbps, requires U3); XAVC HS 4K (280 Mbps, requires V60); XAVC S 4K (280 Mbps, requires V60); XAVC S-I 4K (600 Mbps, requires V90); XAVC S-I HD (222 Mbps, requires V90).
“XAVC HS 4K / XAVC S 4K SDXC V60 or higher XAVC S HD SDHC/SDXC card (U3 or higher) XAVC S-I 4K / XAVC S-I HD SDXC V90 or higher”
Last verified:
Compatibility inferred from spec rule (citations above are manufacturer-verified)