Germany's Siemens is preparing this deal structure because the healthcare division, a maker of gear for medical imaging and lab diagnostics, is not in need of a capital injection, while a stock market listing will give it the option to fund any future takeovers with own shares, the sources added.

Siemens declined to comment.

The engineering group will sell a stake of no more than 20 percent as part of the transaction, which is expected in end-March, two of the sources added.

"Initially, Siemens will certainly not part with 25 percent, more like 15 to 20 percent," one of the sources said.

(Reporting by Alexander Huebner; Writing by Ludwig Burger; Editing by Edward Taylor)