Fio'tak is a hard, ultra-dense, nano-crystalline metal alloy developed by the Earth Caste of the Tau Empire for a variety of applications. Fio'tak is most commonly utilised as the primary constituent of vehicle, aircraft and infantry armour plating. Fio'tak is very resilient to penetration by kinetic strikes or directed energy due to its impact-resistant structure. This material is highly resistant to corrosion by various toxins and other environmental influences and is more lightweight than conventional Imperial materials which serve a similar structural function such as plasteel. When it comes to damage deflection and mitigation, Fio'tak is comparable to the ceramite used in Space Marine Power Armour, but weighs substantially less on a per unit basis.
Fio'tak alloy variants are used by the Tau in a variety of applications, including in infantry armour such as Combat Armour and Recon Armour, Tau skimmer and aircraft vehicle armour, Tau Drones, Tau structures, and the armour of Tau Battlesuits. Battlesuit armour employing Fio'tak is shaped to deflect solid shot, and also has a liquid metal coating that reflects medium-grade laser fire. In some cases, such as that of the XV88 Broadside and XV104 Riptide Battlesuits, additional nano-layers of the material are added to upgrade the armour's thickness so that the protection it offers is even comparable to that of Tactical Dreadnought Armour. The techniques employed in the fabrication of Fio'tak are currently unknown to the Imperium of Man as the Adeptus Mechanicus is officially forbidden from investigating dangerous alien technology by order of the Inquisition's Ordo Xenos.
- Codex: Tau Empire (6th Edition), pp. 40, 70
- Imperial Armour Volume Three - The Taros Campaign, pp. 80, 159, 172, 195
- Fire Warrior (Novel), by Simon Spurrier