The deal with Trafigura and Mubadala Investment Company was announced in late September.
MATSA is a substantial polymetallic mining complex in the Iberian Pyrite Belt, comprising three underground mines and a 4.7 million tonne per annum central processing facility, with cutting-edge technology and infrastructure and an extensive resource base with significant growth potential.
The complex produces about 100,000-120,000 tonnes of copper equivalent per annum at low C1 costs of just 40-50c per pound of copper due to zinc, lead and silver credits.
MATSA's hedge position is 73,878t of copper at $4.19/lb and 84,094t of zinc at $1.31/lb, to be delivered between now and 2025.
The acquisition included 2450sq.km of ground in Spain and Portugal with exploration upside.
The purchase price is being funded from the proceeds of a A$1.2 billion capital raising and US$795 million in debt facilities.
Sandfire has remaining cash of A$384 million.
Managing director Karl Simich, who is in Spain overseeing the integration, described today as an historic day for Sandfire.
"Today marks the beginning of an exciting new era for Sandfire, with our business expanding to an organisation with a workforce of around 3800 direct employees and contractors around the globe," he said.
"This is an incredibly exciting moment for everyone involved with our business, and I would like to take this opportunity to thank everyone who has worked so hard to bring this transaction to a conclusion.
"Our vision for Sandfire is to become an international diversified and sustainable mining company, and the completion of this transaction represents a major step closer to realising this aspiration.
"With the acquisition of MATSA, Sandfire immediately becomes one of the largest copper-focused producers on the ASX, with high-quality operations in Spain and Australia and an impressive growth pipeline and exploration portfolio that we believe will continue to drive our growth for many years to come."
The transaction has already seen Sandfire readmitted to the ASX 200 and its market capitalisation reach more than $3 billion for the first time.
The company plans to provide updated guidance in the coming weeks.
RBC Capital Markets estimates MATSA will generate $317 million in EBITDA for Sandfire in the current half.
"While this marks the completion of the transaction, it represents just the start of our journey with MATSA," Simich said.
"In the days, weeks and months ahead, we will all be working incredibly hard to integrate MATSA into Sandfire to create a single unified team who will be working hard to strengthen the future of the operation and unlock the enormous exploration potential of our large landholding in Spain and Portugal.
"With a larger team, broader expertise and greater capability and strength across our business, we are all looking forward to the vast opportunities that this new chapter will deliver for all of our key stakeholders."
Sandfire operates the DeGrussa mine in Western Australia and is building the Motheo mine in Botswana.
To reflect its increasingly global presence, Sandfire will change its reporting currency from Australian to US dollars from the March quarter onwards.
Shares in the company were up 0.9% to $6.77, valuing it at $2.8 billion. RBC has an outperform rating and $8.75 price target.
