XBT Provider, a Sweden-based bitcoin investment company, has announced its custodial partnership with bitcoin wallet provider Xapo.

With this recent partnership, bitcoin held in cold storage on behalf of investors in XBT Provider’s ETN will now be secured by Xapo.

“The team of professionals at XBT Provider has deep expertise in digital currency and extensive experience in financial services. We are excited to partner with them as they make bitcoin broadly available to investors outside of the U.S.,” said Wences Casares, CEO of Xapo.

“The addition of Xapo to our infrastructure is a critical step in ensuring that our products remain the most professional bitcoin investment products available to investors, globally,” says Ryan Radloff, Head of Investor Relations at XBT Provider.

XBT Provider is the issuer of Bitcoin Tracker One and Bitcoin Tracker Euro, which allows anyone to invest in Bitcoin as ETNs, exchange-traded notes. In its official announcement, the company said its total assets under management doubled in the last 60 days and nearly tripled in the last 6 months, signifying rapidly escalating demand for bitcoin as a portfolio allocation.

“In the last 60 days, XBT Provider’s exchange traded bitcoin note has experienced unprecedented volume in trading and demand from both retail and institutional investors searching for exposure to bitcoin. This trend has quickly doubled assets under management to over the $100 Million threshold,” says Jean-Marie Mognetti, Head of Trading and Operations at XBT Provider.

The partnership follows the recent announcement that Hargreaves Lansdown, the U.K.’s largest broker, listed Europe’s only bitcoin ETN on its digital platform.

Recently, Global Advisors, a Jersey-based hedge fund specializing in digital currency, announced that XBT Group has become its subsidiary.