  Debate over the planet occurrence rates around intermediate-mass stars has
hinged on the accurate determination of masses of evolved stars, and has been
exacerbated by a paucity of reliable, directly-measured fundamental properties
for these stars. We present long-baseline optical interferometry of five
evolved intermediate-mass ($\sim\,1.5\,\mathrm{M}_\odot$) planet-hosting stars
using the PAVO beam combiner at the CHARA Array, which we combine with
bolometric flux measurements and parallaxes to determine their radii and
effective temperatures. We measured the radii and effective temperatures of 6
Lyncis ($5.12\pm0.16\,\mathrm{R}_\odot$, $4949\pm58\,\mathrm{K}$), 24 Sextantis
($5.49\pm0.18\,\mathrm{R}_\odot$, $4908\pm65\,\mathrm{K}$), $\kappa$ Coronae
Borealis ($4.77\pm0.07\,\mathrm{R}_\odot$, $4870\pm47\,\mathrm{K}$), HR 6817
($4.45\pm0.08\,\mathrm{R}_\odot$, $5013\pm59\,\mathrm{K}$), and HR 8641
($4.91\pm0.12\,\mathrm{R}_\odot$, $4950\pm68\,\mathrm{K}$). We find
disagreements of typically 15 per cent in angular diameter and $\sim$200 K in
temperature compared to interferometric measurements in the literature, yet
good agreement with spectroscopic and photometric temperatures, concluding that
the previous interferometric measurements may have been affected by systematic
errors exceeding their formal uncertainties. Modelling based on BaSTI
isochrones using various sets of asteroseismic, spectroscopic, and
interferometric constraints tends to favour slightly ($\sim$15 per cent) lower
masses than generally reported in the literature.
