  A 6-parameter fat-tailed distribution is proposed that generalises the
t-distribution and allows asymmetry of scale and also of tail power, whilst
avoiding the discontinuity of the second derivative of the split-t (AST)
distribution. With the sixth parameter set to unity and no asymmetry, the
distribution reduces to a t-distribution, but with the sixth parameter reduced,
fatter tails than those of the t-distribution are allowed (the tails start
earlier) and the distribution generalises Johnson's $S_U$ distribution. Data
fitting is illustrated with examples.
