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In this and an earlier paper [E.R. van Dam, E. Spence, Combinatorial designs with two singular values. I. Uniform multiplicative designs, J. Combin. Theory A 107 (2004) 127-142] we study combinatorial designs whose incidence matrix has two distinct singular values. These generalize (v, k, λ) designs, and include uniform multiplicative designs and partial geometric designs. Here we study the latter, which are precisely the designs with constant replication and block size. We collect most known results, give new characterization results, and we enumerate, partly by computer, all small ones.

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General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.-Users may download and print one copy of any publication from the public portal for the purpose of private study or research-You may not further distribute the material or use it for any profit-making activity or commercial gain-You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright, please contact us providing details, and we will remove access to the work immediately and investigate your claim.

We characterize the distance-regular Ivanov-Ivanov-Faradjev graph from the spectrum, and construct cospectral graphs of the Johnson graphs, Doubled Odd graphs, Grassmann graphs, Doubled Grassmann graphs, antipodal covers of complete bipartite graphs, and many of the Taylor graphs. We survey the known results on cospectral graphs of the Hamming graphs, and of all distance-regular graphs on at most 70 vertices.

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