  The finite field calculations are performed for two heavy frequency-standard
candidates In$^+$ and Sr. The progressive hierarchy of electron correlations is
implemented by the relativistic coupled-cluster and configuration interaction
methods combined with basis set of increasing size. The dipole
polarizabilities, dipole hyperpolarizabilities, quadrupole moments, and
quadrupole polarizabilities are recommended for the ground state 5s$^2$ $^1S_0$
and low-lying states 5s5p $^3P^{\rm o}_{0,1,2}$ of In$^+$ and Sr. Comparative
study of the fully and scalar relativistic electron correlation calculations
reveals the effect of the spin-orbit interaction on the dipole polarizabilities
of In$^{+}$ and Sr. Finally, the blackbody-radiation shifts due to the dipole
polarizability, dipole hyperpolarizability, and quadrupole polarizability are
evaluated for the clock transition 5s$^2$ $^1S_0$ - 5s5p $^3P^{\rm o}_0$ of
In$^+$ and Sr.
