You/your bank can buy (for you) T-bills (52 week maturities or less) (and not the same as two-year, ten year and longer Treasury notes) in increments as low as $100. The interest rate (difference between purchase price and return at maturity ) is above 4.5%. The dounside of T-bills, unlike regular two year, ten year and longer Treasury notes, is the interest (gain at maturity) is taxable at the federal level. But, the capital is protected and the risk is low to nil.
You can get even a fraction of precent in higher returns (from brokers in the same class as Charles Schwab) if you buy in increments of $10,000 or $25,000 or $50,000.
I'm sure there are places that offer even better returns on increments of $100,000 or a quarter, half or full million. That just doesn't happen to be Schwab's niche.
FWIW, I have spent most of my career working internationally and have seen how microlending has helped lift countries out of third world status-- Japan in the 1950s and 1960s; Singapore in the 1960s and 1970s; Korea and Taiwan in the 1970s and 1980s; Chile when Pinochet took power; then India and Mexico and, now, even Bangladesh in the modern era.
It could even work in the third world parts of America like Indian Reservations and Inner Cities. But it won't because of the types of politicians running these places. Even microlenders expect to get paid back and make a reasonable return.
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All treasury note and treasury bond interest is taxable at the federal level.