The loan to Brazil's BH Airport of roughly US$136mn is for 17 years.
The line will be 21km long and have 16 stations. Construction is 77% complete.
The Brazilian construction group is in talks with Ashmore to sign up to a bond issue.
Brazil's next administration will need to attract the private sector for infrastructure projects given the government's fiscal challenges, says Alexandre Garcia, an infrastructure analyst at Fitch Ratings.
The government signed multiple deals with the private sector to boost the economy, while an official set banks and cooperatives on equal footing in terms of credit cards.