Matlab - Concatenate strings with wildcard -

i have 2 variables, , b, have variable between them creates file name. e.g.

a*b.mat *  %// can number of digits 

obviously dir a*b.mat not work, haven't faintest on how make work.

i think want this: concatenate contents of a , b string '*' in between , '.mat' @ end:

dir( [a '*' b '.mat'] )