The valuation is higher than expected and compares with the pounds 4bn figure previously indicated by the two parent companies.
Shares in Alstom, which is floating simultaneously on the Paris, London and New York markets, will priced in a range of FFr190 to FFr220.
News of the pricing range came as Alstom announced that its board would be strengthened by the appointment of three high-profile non-executive directors, led by Sir William Purves of HSBC, who will be vice-chairman. The other two are Dr Klaus Esser, the vice-chairman of Mannesmann, the German engineering and telecoms group, and Jacques de Laroisiere de Champfeu, the former governor of the Banque de France and managing director of the International Monetary Fund.
GEC and Alcatel intend to float between 52 and 58 per cent of the company. Shareholders in the two parent companies will be entitled to apply for up to 20 per cent of the shares issued which, depending on the level of subscription, could leave them with up to 10 per cent of the company.
Alstom's 110,000 employees will be entitled to apply for a further 2 per cent of the shares at a 20 per cent discount to the strike price.
The strike price will be determined by a single global book building run by CSFB and Goldman Sachs. No tranches of shares will be allocated to any particular geographic market. Nor will there be a public offer of the shares in the UK although French private investors will be able to apply through the global offering.
Alstom, led by its chairman and chief executive Pierre Bilger, will raise 300m ecus of new money from the flotation and is expected to have at least pounds 1bn to play with to finance acquisitions once it is complete.
The company is one of the biggest train manufacturers in the world. It supplies the French TG and Eurostars and is part of a consortium with Fiat which will make high-speed tilting trains for the Virgin West Coast Mainline. Its other interests include power stations, electrical transmission equipment and ships.
Shares in Alstom are due to begin trading on 22 June.