OAS CEO Cesar Mata Pires

OAS CEO Cesar Mata Pires

Artur Ikishima/Editora Abril via Bloomberg

A file photo from 1990 shows OAS SA Chief Executive Officer Cesar Mata Pires. OAS's construction arm accounts for three quarters of its business and Mata Pires's 90 percent stake in the division is valued at $3.6 billion, according to data compiled by Bloomberg.