Although the SEC has recently rejected multiple Bitcoin ETF's, Including the Winklevoss twins, opportunities exist to turn your tax deferred retirement account into a bitcoin investment machine. The vehicle for this is the Bitcoin Investment Trust from Grayscale.
The Bitcoin Investment Trust (GBTC) is not trading on the major US exchanges and this is why it is such a unique opportunity. At the time of this writing, many US investors do not have access to "pink sheet" investments. Many major platforms do not offer this option to consumer investors due to the volatility in these equities. Pink sheets include penny stocks and minors in the mining sector and this is why I have investing with Fidelity for past few years. Fidelity has proven to have more opportunities for the typical retail investor.
GBTC holds .093 BTC for each share and a premium exists above the spot price based on the current demand for the share. With the current upward trend in the bitcoin price, the premium has increased in recent weeks. Personally, I try to set limit orders to purchase in the morning and sell in the afternoon attempting to capitalize simply on the volatility within the bitcoin market.
I will update about additional opportunities in the coming days, including the Bitcoin IRA. Good luck!