With a background as a jazz club owner and manager, Sievernich moved into features as a production manager on "Liebe und Abenteuer/Love and Adventure" (1978) and other German films before connecting with Wenders and Nicholas Ray as producer on "Lightning Over Water" (1979), which recounted the last days of Ray's life. He and Wenders continued their association with "Der Stand der Dinge/The State of Things" (1982), which won the Golden Lion at the Venice Film Festival. On the taut "Paris, Texas" (1984), about a man lost for four years trying to put his life and family back together, Sievernich served as executive producer. Other collaborations with the director include "Chambre 666" (1984) and "Tokyo-Ga" (1985). Sievernich also functioned as a production consultant on "Wings of Desire" (1987), which earned the Palme d'Or at the Cannes Film Festival.
New York became the base for Sievernich's Gray City, Inc., a division of his London-based Nova Films. He has produced two films by Christopher Petit ("Fluchtpunk Berlin/Flight to Berlin" 1983; "Chinese Boxes" 1984) while in 1987, he produced John Huston's final film, the elegiac "The Dead", based on a James Joyce short story. During that film's shoot, he also executive produced the documentary "John Huston & The Dubliners" (1987), a study of the icon's last years, produced and directed by Sievernich's wife, Lilyan. Much of the producer's output in recent years has been filmed in English, from John Schlesinger's period thriller "The Innocent" (1993; released in the USA in 1995) to Trish McAdam's "Snakes and Ladders" (1996), about two female partners in a comedy act whose relationship is threatened when a musician to whom they are both attracted proposes marriage to one of them.