** Shares of American Bitcoin ABTC.O, backed by U.S. President Donald Trump's oldest sons, fall 8.5% to $7.35 premarket a day after their Nasdaq debut
** The bitcoin miner said it has nearly doubled its mining capacity to 24 exahash-per-second (EH/s) from 10 EH/s earlier
** The company is around 20% owned by Eric Trump and Donald Trump Jr, ABTC Executive Chairman Asher Genoot said earlier
** ABTC is among several forays by the Trump family into crypto which has drawn criticisms from Democratic lawmakers and government ethics watchdogs about conflicts of interests
** Eric Trump, the second son of Trump, dismissed such criticisms on Wednesday as "insane"
** In the first day of trading following a SPAC merger, ABTC surged as much as $14.52 before closing at $8.04
(Reporting by Medha Singh)
((medha.singh@thomsonreuters.com))

