Question: What opera company has its permanent home as he Staatsoper Unter den Linden and had Franz Betz as an opera singer in the 1800's?
Sentence (from "Klaus Häger"): Häger has sung in Lieder recitals and made numerous recordings for German television, and has also performed at festivals such as Salzburg Festival, Schwetzingen Festival, Schleswig-Holstein Musik Festival and Ludwigsburg Festival.
Relevant evidence: No