The pair will become co-worldwide heads of European sculpture and works of art.
Kader has been at Sotheby’s since 1996 and head of the London sculpture department since 2000.
Schwartz joined in 1986, was promoted to head of the European works of art department in 1992, and became an auctioneer in 2005.
They have been promoted to lead the strategy for the company in sculpture sales across North and South America and Europe.
From Sotheby’s New York office, Schwartz will focus on high end consignments and collections and will remain the worldwide senior lead specialist for sculpture at the auction house.
In London Kader will focus on Europe, particularly its London and Paris departments.
Sotheby’s auctions of Old Master Sculpture and Works of Art are held twice annually in July and December, while masterpieces with noble provenances are offered in the Treasures sale in July. Alongside these auctions, sales of 19th and 20th century sculpture are held in June and December.
Recent significant private sales include the marble bust of Pope Paul V by Gian Lorenzo Bernini to the Getty Museum.