Iodate nitrate
Iodate nitrates are mixed anion compounds that contain both iodate and nitrate anions. Giant birefringence
Iodate nitrates can have high birefringence. The scandium salt has a giant birefringence of 0.348 at 546 nm. When discovered in 2021 it was a record high birefringence for oxyanion compounds, but it was exceeded by CeF2(SO4) just a month later with a value of 0.361 and sodium hydrogen squarate hydrate, NaHC4O4·H2O with a value of 0.52 at 1064 nm. All of these are beaten by hexagonal boron nitride (h-BN) with birefringence of 0.7 in visible light. List

References

Iodates
Nitrates