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A new family of noncentrosymmetric rare earth crystals have been synthesized by a ternary anion‐engineering strategy that integrates π‐conjugated carbonate, non‐π‐conjugated sulfate, and lone‐pair‐electron‐containing hydroxyl group. These crystals exhibit wide deep‐UV transparency with an absorption edge below 190 nm, a strong SHG response with an intensity 2.5 times that of Y‐cut quartz at 860 nm and a suitable birefringence of 0.023@1064 nm. More details are discussed in the article by Zhang et al . on pages 1743—1752. image