The agency is advising Portuguese clean energy company EDP Renovaveis ahead of its 4 June listing on Euronext Lisbon.
Citigate also worked on the IPO for New World Resources, now the second largest of the year, completing at 1.6bn euros.
EDP Renovaveis, a brand of Portuguese energy giant EDP, is expected to raise up to 2bn euros.
The economic downturn has led to less IPO and merger activity in the market in 2008.
Figures from the London Stock Exchange showed the market value of IPOs in London has slipped by 80 per cent this year, compared with the same period in 2007 (PRWeek, 20 March).
EDP Renovaveis is the world's fourth largest global renewable energy company, with a focus on onshore wind farms.
It is the fastest growing of its kind, based on installed capacity, with development projects planned for growth markets including the US and Spain.