I know of Martinez, journalist, novelist and university lecturer, only through his novel The Tango Singer. The narrator, trying to follow a mythic singer whose performances in unexpected places in the city may or may not relate to the stories of Borges, finds himself passing through some of the stories and landscapes, many of them violent, of the history of Argentina from its founding, through the military period and into the 2002 financial crisis, stories upon stories within stories.
He lived through the worst years of Latin American history in exile. There's an interview with him by Maya Jaggi here.
PS. There's a Guardian obituary here.