Hamburger SV sport director Frank Arnesen has taken over as coach of the Bundesliga club.
Hamburg, botoom of the Bundesliga, said on their website that Arnesen will fulfill both roles until a permanent replacement can be found for Michael Oenning, who was fired last month.
"I'll do the job until the coach who is best for Hamburg is there," Arnesen said. "Even if takes until the winter."
Interim coach Rodolfo Cardoso's work permit expired on Saturday, after the German league denied a request to allow the Argentine to continue without the necessary coaching licence.
The league said there were "no extenuating circumstances" to allow Cardoso to remain in charge beyond the permitted 15 days. However, the 55-year-old Arnesen has the necessary license, earned in 2002 after completing the courses and exams in the Netherlands.
"I worked hard for everything," said the former Denmark international, who will be assisted by Frank Heinemann and Cardoso.
Cardoso led Hamburg to its first win of the season against Stuttgart and was unlucky to see the side lose to Schalke 2-1.
"I won't change much," Arnesen said. "We've just played our two best games this season. We're on the right path."
Hamburg has been linked with a host of possible candidates, including Huub Stevens, who was appointed Schalke coach, former Netherlands coach Marco van Basten, and most recently former Bayern Munich player Thorsten Fink, who reportedly remains Arnesen's first choice to take over.
The 43-year-old Fink is currently coach of FC Basel, which he led to two Swiss league titles and one cup win. His contract with the Swiss champions runs to 2013.
Kicker magazine reported Basel's vice president Bernhard Heusler as saying Sunday: "Our refusal was made, and Hamburg accepted it."
Arnesen said he went through "all the possible alternatives and came to the conclusion that the right coach for Hamburg is currently not available."
"I also have to have the feeling that he fits, that he can make the team better, and that I can work together with him," Arnesen said. "I want the best coach for Hamburg and don't want to take the second or third choice just to present a solution."
Hamburg has never been relegated from the top division, and is the only team to have played in the Bundesliga continuously since it was formed in 1963.
Germany great Franz Beckenbauer, who had a two-year spell at Hamburg from 1980-82, recently said there was "no coach in the world who can help Hamburg."
"The new coach would have to be a wizard ... A normal being has no chance in the short term," Beckenbauer said.
Arnesen's first game in charge will be at Freiburg on Sunday.