New Investment: U.S. Treasury Bills

Interactive Brokers currently pays 1.7% interest on U.S. Dollars. But U.S. government bonds pay more than that and are supposedly risk free, so I thought I would give it a try. I am concerned that U.S. interest rates could still rise and so I don't want longer term bonds. So, I just bought a U.S. Treasury Bill expiring on 12 February. My idea is when that matures, I'll put part of the proceeds towards buying Australian Dollars. I plan to build a ladder of these and so force myself to buy Australian Dollars slowly.

At IB the commission for buying bonds is $5 and it turns out that the minimum trade size for treasuries is $100k. This isn't stated anywhere, but when I tried buying $50k last week, I got a message that my trade size was too small, whereas this trade went through. I'm gradually moving U.S. Dollars to my IB account - I can move up to $100k every 7 business days using the ACH method.

I've thought about municipal and corporate bonds too, but these can be illiquid. For example, for the nearest term Berkshire Hathaway bond, only $1000 is currently being offered.