Rainer Bock, who plays Officer Keller (Astrid's boss) on Homeland's episode 5.5, Better Call Saul, played Werner Ziegler (German engineer who built Gus Fring's underground lab) on the TV series Better Call Saul.
Both Nina Hoss (Astrid) and Rainer Bock, who plays Officer Keller (Astrid's boss) Homeland played German intelligence officers - in a very similar relationship - in "A Most Wanted Man" (based on the John Le Carre novel.