Craig Wright, chief scientist at nChain and the man who claimed to have invented the cryptocurrency Bitcoin, is being sued for $10 billion by the estate of his former business partner Dave Kleiman.

Filed in a Florida court on February 14th the lawsuit, first reported by tech site Motherboard, alleges that Wright “perpetrated a scheme” to “seize Dave’s bitcoins”.

An Australian now living in London, Wright went public in late 2015 claiming to be Bitcoin creator Satoshi Nakamoto, although he later backed down from substantiating the claim. Wright mined bitcoins with Kleiman, a programmer who died in 2013.

Dave Kleiman’s estate, represented by his brother Ira, says that while the total amount of Bitcoin in question is unknown it’s thought to be between 300,000 and 1.1m Bitcoin.

“It is unclear whether Craig, Dave, and/or both created Bitcoin,” the lawsuit says.

“It is undeniable, however, that Craig and Dave were involved in Bitcoin from its inception, and that they both accumulated a vast wealth of Bitcoins from 2009 through 2013.”

It alleges that, at the time of Kleiman’s death “no one in his family was aware of the extent of his involvement in creating Bitcoin … recognising this, Craig perpetrated a scheme against Dave’s estate to seize Dave’s Bitcoins and his rights to certain intellectual property associated with the Bitcoin technology”.

It also claims Wright later used forged documents to make Kleiman’s family believe Kleiman had given Wright full ownership of a company the two founded, the cyber security-focused W&K Info Defense Research.

When Ira Kleiman later questioned the documents, Wright told him he would be “paid out of what was owed to Dave’s estate”, but according to the court filing those payments never came.

Kleiman’s estate is seeking the value of the bitcoins Wright and Kleiman supposedly mined in the early days of the currency, as well as the intellectual property owned by W&K.

They estimate the value of those assets “far exceed $5,118,266,427.50”.