Cash in SIPPs and ISAs

Happy New Year all.
We can get reasonable interest on fixed rate cash bonds, eg 3.1% for 5 years.
It annoys me, and I think it outrageous that banks and BSs offer lower rates for cash in ISAs. Any "good" reason, other than they can get away with it?
I would like to hold cash in some of my SIPPs in fixed rate bonds, eg the 3.1% for 5 years - but this seems impossible. I assume the reason why these are not offered is there is little in it for Hargreaves Landown, Cavendish, III, etc, as these rates will be very competitive. OK, the ~0.5% SIPP fee would come off, but I could live with that.
Is there a way of holding cash bonds in a SIPP? Does any SIPP provider offer this? The only way I can think of is to buy (relatively short maturity) Treasuries, but those rates are worse than retail cash bonds.
I'm just trying to make my SIPP portfolio a bit more defensive / conservative.
Thanks in advance, Fred
Reply to
investor

BeanSmart website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.