Forcing variables types when using read.table

Perhaps I am being thick, but I can not figure out how to force read.table to
treat as character something that "looks" numeric to it. Here is a simple example:

version

_                   
platform sparc-sun-solaris2.6
arch     sparc               
os       solaris2.6          
system   sparc, solaris2.6   
status                       
major    1                   
minor    3.0                 
year     2001                
month    06                  
day      22                  
language R

file.show("temp.txt")

sedol,price
000312,47
071290,112

read.table("temp.txt", header = TRUE, sep = ",")

sedol price
1   312    47
2 71290   112

read.table("temp.txt", header = TRUE, sep = ",", as.is = TRUE)

sedol price
1   312    47
2 71290   112

Note that "sedol" is really a character string (it is an international
identifier for stocks) while price is numeric. How can I get read.table to
create sedol as character (and therefore keep around the leading zeroes)? I
guess that I am looking for an option like "what" from scan . . .

Thanks,

Dave Kane 
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