German research firm GfK names new chairman amid M&A talk

* GfK Verein board member named as new GfK (Swiss: GFK.SW - news) chairman

* Chairman and CEO had quit over strategy tussle

* Magazine reports GfK Verein could sell its GfK stake

* Nielsen (EUREX: 11400372.EX - news) , IMS Health (Frankfurt: A1XFVF - news) , WPP (Frankfurt: A1J2BZ - news) interested - WirtschaftsWoche

* Shares (Berlin: DI6.BE - news) in GfK jump as much as 8.4 percent (Recasts with new chairman, adds analyst comment)

By Maria Sheahan and Alexander Hübner

FRANKFURT, Aug 25 (Reuters) - German market research firm GfK named an executive from its main shareholder as its chairman on Thursday, on the same day a magazine reported the shareholder was considering a sale or merger for GfK.

Shares in GfK rose more than 8 percent after German weekly WirtschaftsWoche said GfK Verein, the non-profit think tank that owns 56.5 percent of GfK, was considering options for the firm.

The magazine, without citing sources, said U.S (Other OTC: UBGXF - news) . rivals Nielsen Holdings (Frankfurt: NHL.F - news) and IMS Health as well as WPP (Swiss: OXWPP.SW - news) unit Kantar were interested in GfK, which is best known for its consumer confidence indices and TV audience ratings.

GfK Verein and Nielsen were not immediately available for comment on the report. GfK itself, which is worth around 1 billion euros ($1.1 billion) on the stock market, declined to comment, as did IMS Health and WPP.

Separately, GfK said Ralf Klein-Boelting, 54, would take over as chairman, replacing Arno Mahlert who resigned this month after falling out over strategy with GfK Verein.

Klein-Boelting, set to start his job on Sept. 13, said in a statement his top priorities would be to strengthen GfK's operational business and find a new chief executive to replace Matthias Hartmann, who has also resigned.

GfK has struggled to stop a slide in underlying profit margins that analysts have blamed on operational problems and management's failure to deal with sales volatility.

Earlier this month, GfK warned on 2016 profits for a second time, sending its shares tumbling about 20 percent. {nL8N1AT1UQ]

Klein-Boelting, a former marketing expert at rail operator Deutsche Bahn and mail-order retailer Otto, has spent seven years on the executive board of GfK Verein.

"We used to believe that GfK Verein would hold on to its stake in GfK SE (LSE: 0JWU.L - news) forever, but it has been clear for a few months that GfK on a stand-alone basis has a long way to go before reaching previous profitability levels again with AOI (adjusted operating income) margins of 15 percent," Bankhaus Lampe analyst Christoph Schlienkamp said.

He calculated a price target of around 50 euros for GfK, based on a possible break-up and the valuation of Nielsen.

The stock was up 5.3 percent at 28.95 euros by 1305 GMT, outperforming a 0.6 percent lower German small-cap index .

GfK Verein was founded in 1934 in response to Germany's economic crises of the 1920s. Its membership consists of hundreds of companies and a few individuals who receive basic annual statistics on the German economy for a small fee.

($1 = 0.8875 euros) (Reporting by Maria Sheahan; Additional reporting by Hans Seidenstuecker; Editing by Madeline Chambers and Mark Potter)