Invest News DetailReuters - A price range of 3.90 to 4.70 lira has been set for an initial public offering of Turk Telekom, valuing the operator at up to 16.45 billion lira ($12.9 billion), the Privatisation Administration said. The Administration said in a circular published on Sunday that book-building would take place between April 28 and 30. Turk Telekom, which was partly privatized in 2005, is listing a 15 percent stake or 17.25 percent including an over-allotment option. The government is pressing ahead with the deal despite a 22 percent slide on Istanbul's main stock index this year which has prompted several IPOs to be postponed. A 16.45 billion lira market value, or $12.85 billion at current conversion rates, compares with the $11.91 billion at which the company was valued in 2005 by the first deal in its privatisation process, when Dubai-based Oger Telecom paid $6.55 billion for a 55 percent stake. Sixty-five percent of the offering will be aimed at foreign institutional investors. Deutsche Bank and Garanti Securities, part of Garanti Bank are advising on the offering.