ATH Resources, one of the UK's largest coal producers, has won a new sales contract to supply EDF Energy, one of the UK's biggest home and business energy suppliers, with 350,000 tonnes of coal.
The Doncaster-based company said the coal will be supplied at prices linked to international market indices.
Supply will commence immediately and end in December 2012.
Alistair Black, chief executive of ATH Resources, said: "This contract is an important development for ATH as it will increase average sales prices at the same time as the group continues to supply the remainder of its fixed price contracts.
"The existing fixed price contracts that the group has in place will start to be phased out from March 2012."
Last week ATH said it is on a much more stable footing after selling its regeneration business.
The mining group said after a "difficult year", which saw pro?ts and coal production fall, its growing coal reserves and renewed focus give it grounds for optimism.
Publishing its ?rst results since former chief executive Tom Allchurch and ?nance director Steven Beaumont bought out its regeneration arm in a private equity-backed venture, ATH said its proved reserves of coal stand at a record 6.1m tonnes.
It has planning permission for two new Scottish surface mines, Netherton and Duncanziemere, adding 4m tonnes to its reserves and taking its total reserves to 8.6m tonnes.
"We see some significant earnings growth going forward as some of the older contracts work out of the system," said executive chairman David Port.
"Selling the group's regeneration business... has reduced the volatility of the group's earnings."
The group was hit by heavy rainfall last winter, followed by snowfall and freezing temperatures, which slowed production.