Coma and current race leader Cyril Despres have been locked in a see-saw battle this year, just as in previous editions, but today it was the Spaniard who triumphed, clawing back two minutes and three seconds with the stage win.
"It is common knowledge that the stage before the rest day is always difficult," Coma said afterwards, "and today was not an exception, with stifling heat and very soft sand. Nevertheless, we rode very fast and I was able to attack."
Frenchman Despres retains a seven minute, 48 second advantage in the overall classification after a watchful stage ride in which he matched Coma's pace until the closing stages.
"I was a bit lazy today," Despres claimed, "since Marc led the race from km 200 onwards, the start of the second special, but I think that is also part of the race.
Behind the leading duo Portugal's Paulo Goncalves picked up a podium finish a further 46 seconds adrift of Coma, while compatriot Helder Rodrigues, grabbed fourth.
Rodrigues is the best of the rest of the field in the overall standings, already more than 40 minutes behind the battle between the duo who have, between them, won every staging of the Dakar Rally since 2005.
The competition breaks for a rest day on Sunday before resuming with stage eight from Copiapo to Antofagasta on Monday.