<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The new title compounds are prepared under high‐pressure/high‐temperature conditions from Ln<sub>2</sub>O<sub>3</sub> (Ln: Tb, Dy, Ho), LnF<sub>3</sub>, and B<sub>2</sub>O<sub>3</sub> (multianvil press, BN crucible, 900—1200 °C, 1.5—3 GPa).</p> </abstract>