* Wacker's polysilicon EBITDA margin 40.9 pct vs 51.8 pct
* Centrotherm Q1 oper loss 42.9 mln eur vs 7.3 mln forecast
* Wacker Chemie shares down 5.8 pct, Centrotherm down 11.2 pct (Adds Centrotherm, updates share prices)
By Christoph Steitz
FRANKFURT, May 4 (Reuters) - Wacker Chemie and Centrotherm, showed the effects of a solar industry shake-out, with earnings and margins coming under pressure as falling government incentives for solar power and cheap Asian rivals squeeze western peers.
Wacker Chemie - the world's second-biggest maker of polysilicon, a key component needed to make solar cells - said profit margins at its polysilicon unit fell significantly in the first quarter due to high raw material costs and low selling prices.
Polysilicon is used by makers of solar cells, which have come under intense pressure from fierce competition from Asian rivals, overcapacity and falling government subsidies for solar power, driving some players out of business.
Centrotherm, the world's second-biggest maker of solar equipment, posted a bigger-than-expected operating loss in the first quarter, blaming the ongoing turbulence in the market that has claimed companies including Q-Cells and Solon .
"The sector is experiencing its most severe crisis to date, and consolidation is fully underway," Centrotherm's Chief Financial Officer Thomas Riegler said in a statement on Friday.
At 1112 GMT, shares in Wacker Chemie were down 5.8 percent, at the bottom of Frankfurt's midcap index, while Centrotherm shares were down 11.2 percent, the biggest decliner in the technology index.
Wacker Chemie said the operating margin in its polysilicon business narrowed to 40.9 percent from 51.8 percent in the year-earlier period.
The company's polysilicon business is an important profit driver and last year accounted for about 30 percent of group sales and more than two-thirds of earnings before interest, tax, depreciation and amortisation (EBITDA).
"The price decrease was significant," DZ Bank analyst Peter Spengler said, keeping a "hold" rating on the stock.
Wacker's main rivals in the production of polysilicon include Hemlock Semiconductor, a joint venture between Dow Corning, Shin-Etsu Handotai and Mitsubishi Materials, as well as Korean OCI Co Ltd and China's GCL-Poly Energy Holdings.
Wacker said last week that demand for polysilicon rebounded in the first months of 2012, yet prices would be below year-earlier levels.
The group said first-quarter sales were 1.19 billion euros ($1.57 billion), beating the 1.16 billion average forecast in a Reuters poll of analysts. EBITDA was 212 million euros, in line with the forecast.
Centrotherm said its loss before interest and tax was 42.9 million euros ($56.4 million), wider than the 7.3 million euros Thomson Reuters I/B/E/S estimate. ($1 = 0.7603 euros) (Additional reporting by Daniela Pegna; Editing by Erica Billingham)