Thank you, Roberta. Good morning, and good afternoon, everyone. I am now on Slide 13. As demonstrated in the upper left graph, our liquidity remains strong, and we continue to report a healthy balance sheet with extended debt profile. By the end of the first quarter, our available liquidity was $1.3 billion, which includes our undrawn revolving credit facility of $300 million.
As of March 31, the average maturity of our total debt was 5.3 years, with an average debt cost of 4.7%. Our leverage, measured by the net debt-to-adjusted EBITDA ratio decreased to 1.73x from 2.29x, mainly driven by the recovery of our cash generation, replacing a much lower first Q of 2020.
The debt breakdown graphs are shown on the right side of the slide, both by debt category and by currency. Now moving to Slide 14. For 2021, our investment guidance remains unchanged. In the first quarter, we invested $84 million in CapEx. The Aripuanã project amounted to $40 million, 50% of total approximately. For the year, as previously disclosed, we estimate to invest $232 million to further develop Aripuanã. Sustaining investments, including HSE amounted to $31 million in the quarter.
As projects advance, we expect disbursements to increase over the quarters, meeting guidance. In terms of mineral exploration and project evaluation, we invested a total of $14 million in the quarter. For 2021, we expect to continue our mineral exploration and project evaluation investments as we will maintain our efforts to replace and increase mineral reserves and resources, supporting our business growth.
As we anticipated to the market, this quarter, we published our first exploration report. I encourage all of you to read it and hope the document provides further clarity on our exploration program strategy and its results.
Turning now to the next slide, Slide 15. On this slide, we present Nexa's free cash flow generation. During the quarter, we consumed $80 million of our liquidity. Describing it further and starting from our $180 million adjusted EBITDA, we had a $13 million gain in working capital, which was more than offset by sustaining CapEx, interest paid and taxes. Still, Nexa has generated $105 million of cash flow before expansion projects during the annualized period.
After that, we invested $52 million in nonsustaining CapEx, which includes mainly our Aripuanã development project. Also, we had $42 million from loans due in the quarter, $6 million of the acquisition of 9% equity interest in Tinka Resources, $33 million in net dividend payments and finally, other nonoperational impacts of $51 million, including FX.
I will now hand the call back to Tito. Tito, please.