BOGOTA (Reuters) - Colombia s notorious Golfo Clan crime gang, one of the country s most violent, has told the government it is willing to surrender, President Juan Manuel Santos said on Tuesday. The group, also known the Usuga Clan, is accused of operating profitable drug trafficking routes in partnership with Mexican cartels and taking part in illegal gold mining.   We received an expression of willingness by the head of the Golfo Clan to turn themselves in, to submit to justice,  President Juan Manuel Santos said at an event in Bogota.  I have asked the justice minister and the attorney general to evaluate it.  The government is not going to negotiate with the gang, Santos said, because members are criminals, and not politically motivated rebels like the FARC and ELN guerrilla groups.  The group formerly known as the Revolutionary Armed Forces of Colombia, who have kept their FARC acronym for their new political party, signed a peace deal with the government last year, while the National Liberation Army (ELN) is in peace talks.  If they surrender to justice, the law could give them some benefits, depending on the surrender conditions,  Santos said.  What are they handing over, what is its value to society, for Colombians.  The United States has offered a reward of up to $5 million for information leading to the capture of Golfo gang leader Dario Antonio Usuga, known by his alias Otoniel.    Second-in-command Roberto Vargas, alias Gavilan, was killed by the army in a shoot-out last week. The group is infamous for a series of police officer assassinations in the Andean country. 