Ivancev is accused of participating in a conspiracy to gather information that could be useful, directly or indirectly, to an enemy.
The information he collected appears to be aimed at damaging national security and undermining the state's interests.
A resident of Acton in west London, Ivancev has been remanded in custody and will appear in court on Feb. 28.
The suspect was arrested and identified as part of an ongoing investigation that led to the previous five arrests in this case. He now faces charges brought by the Crown Prosecution Service.
The other three male and two female defendants — Orlin Rusev (46), Biser Dzhambazov (42), Katrin Ivanova (32), Ivan Stoyanov (32), and Vanya Gaberova (29) — are charged with conspiring from August 2020 to February 2023 to gather information for the benefit of an adversary.
The five have already appeared in court at the Old Bailey, with their trial set to begin in October.